Add BingTileLayer to get map tiles from Bing

Based off of https://github.com/osmdroid/osmdroid/blob/master/osmdroid-third-party/src/main/java/org/osmdroid/tileprovider/tilesource/bing/imagerymetadata/ImageryMetaDataResource.java
Updated docs/_layouts/default.html
#525 - Added native rotation abilities to MapView
Merge pull request #519 from kjeremy/bing

Add BingTileLayer to get map tiles from Bing
#483 - Fixing checkstyle issues
Merge pull request #536 from loicortola/mb-pages

#525 - Added gesture detector library from Almeros, added native rotation abilities to MapView
#525 - Fixing checkstyle issues in order to push snapshot build
#537 - Setting up test / demo of PathOverlay
#537 - Creating green to yellow linear gradient inside pathoverlay
Updated docs/_layouts/default.html
#540 - Adding GeoUtils and findBoundingBoxForGivenLocations() method
#533 - Merge branch 'mb-pages' of github.com:mapbox/mapbox-android-sdk into offline

Conflicts:
	MapboxAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/android/testapp/MainActivity.java
	MapboxAndroidSDKTestApp/src/main/res/values/strings.xml