Move everything from library/ folder to top-level, to prevent module name clashes in Android Studio.
Add support for Android Studio.
Add support for empty state (ContentState.EMPTY).

    * Useful in cases where the content depends on user actions: when there is no content to show, an empty state notifying the user of the same looks better than a completely blank view.

    * The library doesn't play well with AbsListView#setEmptyView(), so this is a good alternative.
Fix incorrect documentation on some XML resources.