java.lang.NoClassDefFoundError: com.squareup.picasso.Picasso

android studio 2.0preview。gradle插件：2.0.0-alpha3
使用的代码如示例中的： SliderLayout sliderShow = (SliderLayout) mainActivity.findViewById(R.id.slider);
TextSliderView textSliderView = new TextSliderView(mainActivity);
textSliderView
.description("Game of Thrones")
.image("http://images.boomsbeat.com/data/images/full/19640/game-of-thrones-season-4-jpg.jpg");

```
sliderShow.addSlider(textSliderView);
```

然后就出现如下错误。求指正！
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: java.lang.NoClassDefFoundError: com.squareup.picasso.Picasso
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.SliderTypes.BaseSliderView.bindEventAndShow(BaseSliderView.java:210)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.SliderTypes.TextSliderView.getView(TextSliderView.java:25)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.SliderAdapter.instantiateItem(SliderAdapter.java:81)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.Tricks.InfinitePagerAdapter.instantiateItem(InfinitePagerAdapter.java:54)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.Tricks.ViewPagerEx.addNewItem(ViewPagerEx.java:848)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.Tricks.ViewPagerEx.populate(ViewPagerEx.java:998)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.Tricks.ViewPagerEx.populate(ViewPagerEx.java:930)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.daimajia.slider.library.Tricks.ViewPagerEx.onMeasure(ViewPagerEx.java:1453)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:610)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:677)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.View.measure(View.java:16529)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1973)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1170)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1352)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1057)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5666)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.Choreographer.doCallbacks(Choreographer.java:574)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.Choreographer.doFrame(Choreographer.java:544)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.os.Handler.handleCallback(Handler.java:733)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.os.Handler.dispatchMessage(Handler.java:95)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.os.Looper.loop(Looper.java:136)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5072)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at java.lang.reflect.Method.invokeNative(Native Method)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at java.lang.reflect.Method.invoke(Method.java:515)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
01-13 18:41:51.947 31958-31958/com.gc.parcool W/System.err: at dalvik.system.NativeStart.main(Native Method)