Fixes test errors resulting from vtm-android update.

* Renames ItemizedIconLayer -> ItemizedLayer in MapFragmentTest.
* Returns a new TestMap via getMap() in ShadowMapView.
* Registers TestMap via MapView in TestHelper.initBaseActivity().
* Renames getViewport() -> viewport() in TestMap.
* Adds @Config(emulateSdk = 18) to all test classes (Robolectric does not yet support API 19).
* Fixes checkstyle errors in Feature and MapFragment.
Merge pull request #33 from mapzen/vtm-android-gradle-update

Fixes test errors resulting from vtm-android update.