fix CachingHTTPFileSource::clearLoop
Merge pull request #721 from mapbox/clear-loop

fix CachingHTTPFileSource::clearLoop
indicate submodule setup in common header of install info
Update READMD.md for OS X Yosemite
Make file request overridable by platform implementations

refs #579: Android can now rename AssetRequest to FileRequest and implement it differently
change file:// to asset:// to indicate that they aren't arbitrary files

refs #579
change comment and cache value
Merge pull request #723 from mapbox/overridable-file-request

Make FileRequest overridable by platform implementations
Merge branch 'master' of github.com:mapbox/mapbox-gl-native into android-mason

Conflicts:
	gyp/mbgl-ios.gypi
	gyp/mbgl-osx.gypi
	platform/default/asset_request_libuv.cpp
	src/mbgl/storage/caching_http_file_source.cpp
	src/mbgl/storage/file_request.cpp
	src/mbgl/storage/file_request.hpp
	src/mbgl/storage/file_request_baton.hpp