Adds Shadow class for Android Support Library r18's DrawerLayout.

* Adds ShadowDrawerLayout including ability to mock opening & closing of DrawerLayout.
* Adds DrawerLayout unit tests.
* Changes dependency for Android compatibility lib from r7 to Android Support Lib r18.
Merge branch 'shadow-drawerlayout' of https://github.com/aweber/robolectric into display_impl
Use min/max for getCurrentSizeRange implementation