Add gcc back to build matrix (fixes #465)
Update Ubuntu instructions in README [skip ci]
fix 64-bit iOS builds
bump Cocoa
bump Cocoa for location fixes
bump Cocoa one more time
Refactor tile cover to match JS
Support pixelRatio parameter for render tests
transition-* ⇢ *-transition

https://github.com/mapbox/mapbox-gl-style-spec/issues/148
add basic request caching with sqlite
remove access token from URL
also store other response codes in the cache
compress data and store type
parse cache-control and last-modified headers
don't report SQLITE_OK as an error
add missing headers
link dependencies with sqlite3
fix issue that deleted the data part of a std::string as a std::string object
add libcurl build
fix build issues