add jpeg lib
add image_reader abstraction layer to hanfle multiple image formats
(work-in-progress)
Merge branch 'master' into image-readers
Merge branch 'master' into image-readers
add cflags for linux builds
move image_reader to mbgl-linux
fix tests for linux (todo - find a better way to run 'linux' tests on 'osx')
"skip install" for lib Xcode targets for easier app archiving
cleanups
Merge branch 'master' into image-readers
pass png_static_libs to other_ldflags in install.gypi on Linux, closes #581
Merge pull request #600 from mapbox/png-other-ldflags

pass png_static_libs to other_ldflags in install.gypi on Linux
fix linux build
remove unused pragmas
simplify factory class to not rely on singleton + cleanups
remove travis default installed libs which might conflict
Revert "remove travis default installed libs which might conflict"

This reverts commit 23d3588f500f79cc5f532ae7aaf687aaacd6568d.
use nunicode conditional case mapping (lowercase)
fix png_reader
image-readers: only register readers that are used

create_png_reader(char const* data, size_t size)
create_jpeg_reader(char const* data, size_t size)