Add application tag to AndroidManifest.xml

In order to use Robolectric library there is a need to have <application \> tag defined in the android manifest.

relative pull https://github.com/robolectric/robolectric/pull/1309

library/src/main/AndroidManifest.xml

@@ -1,4 +1,5 @@
 <manifest package="com.afollestad.materialdialogs">
+ 
+    <application />
 
-
-</manifest>
+</manifest>