Reflective setting of gravity throws exception, dumping stacktraces in logs

I am using SwipeLayout with [macroid](https://github.com/47deg/macroid) in scala, so the SwipeLayout is created via code. It works great, but it fills the logs with exceptions, due to the following line:

https://github.com/daimajia/AndroidSwipeLayout/blob/d7a5759784c7399a1cbfe9b62c9fa6d0f257ab52/library/src/main/java/com/daimajia/swipe/SwipeLayout.java#L752

```
W/System.err(17183): java.lang.NoSuchFieldException: gravity
W/System.err(17183): at java.lang.Class.getField(Class.java:1138)
W/System.err(17183): at com.daimajia.swipe.SwipeLayout.addView(SwipeLayout.java:684)
W/System.err(17183): at android.view.ViewGroup.addView(ViewGroup.java:4064)
W/System.err(17183): at android.view.ViewGroup.addView(ViewGroup.java:4037)
```