Migrate to AndroidX

We are using this library since long time and it works great. We have recently [Migrating to AndroidX](https://developer.android.com/jetpack/androidx/migrate), although by adding `android.enableJetifier=true` and `android.useAndroidX=true` in `gradle.properties` converts all support package of dependency at build time. The stable release of 28.0.0 will be the final feature release packaged as android.support. All subsequent feature releases will only be made available as androidx-packaged artifacts. [ For more detail please check.](https://android-developers.googleblog.com/2018/05/hello-world-androidx.html) I suggest you to update the library with AndroidX to avoid confusion.