Added Mapbox credits
Added Mapbox credits

This is my understanding of what the rules at https://github.com/mapbox/mapbox-gl-native/edit/master/LICENSE.md require us to do.
misaochan/apps-android-commons,dbrant/apps-android-commons,maskaravivek/apps-android-commons,commons-app/apps-android-commons,nicolas-raoul/apps-android-commons,maskaravivek/apps-android-commons,neslihanturan/apps-android-commons,domdomegg/apps-android-commons,misaochan/apps-android-commons,whym/apps-android-commons,neslihanturan/apps-android-commons,dbrant/apps-android-commons,commons-app/apps-android-commons,psh/apps-android-commons,whym/apps-android-commons,nicolas-raoul/apps-android-commons,maskaravivek/apps-android-commons,nicolas-raoul/apps-android-commons,maskaravivek/apps-android-commons,whym/apps-android-commons,psh/apps-android-commons,nicolas-raoul/apps-android-commons,commons-app/apps-android-commons,misaochan/apps-android-commons,psh/apps-android-commons,neslihanturan/apps-android-commons,misaochan/apps-android-commons,misaochan/apps-android-commons,domdomegg/apps-android-commons,whym/apps-android-commons,neslihanturan/apps-android-commons,misaochan/apps-android-commons,domdomegg/apps-android-commons,dbrant/apps-android-commons,commons-app/apps-android-commons,domdomegg/apps-android-commons,dbrant/apps-android-commons,domdomegg/apps-android-commons,psh/apps-android-commons,neslihanturan/apps-android-commons,commons-app/apps-android-commons,psh/apps-android-commons,maskaravivek/apps-android-commons