Add Android Arseal Badge

Author: ivan.navas

README.md

@@ -2,6 +2,8 @@
 
 # Material Design Android Library
 
+[![Android Arsenal](https://img.shields.io/badge/Android%20Arsenal-Material%20Design%20Android%20Library-brightgreen.svg?style=flat)](https://android-arsenal.com/details/1/1156)
+
 * [How to use](#howtouse)
 * [Components](#components)
     * [Buttons](#buttons)