Update for CI. Includes Checkstyle in gradle build script and adds the
sdk-manager-plugin for automating CI setup.

To let Travis Build, this commit:

* Formatted the code with updated code styles
* Fixed any glaring checkstyle erorrs
* Suppresses some checkstyle modules
Merging for #319

Merge branch 'ci-stuff' of https://github.com/f2prateek/mapbox-android-sdk into f2prateek-ci-stuff

Conflicts:
	MapboxAndroidSDK/src/main/java/com/mapbox/mapboxsdk/format/GeoJSON.java
	MapboxAndroidSDK/src/main/java/com/mapbox/mapboxsdk/overlay/GeoJSONLayer.java
	MapboxAndroidSDK/src/main/java/com/mapbox/mapboxsdk/tileprovider/tilesource/MapboxTileLayer.java
	MapboxAndroidSDK/src/main/res/values/attrs.xml
	MapboxAndroidSDKTestApp/src/main/AndroidManifest.xml
	MapboxAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/android/testapp/MainActivity.java
	MapboxAndroidSDKTestApp/src/main/res/layout/activity_alternatemap.xml
Merging for #319