use unique_ptr for automatic deallocation
do not crash for missing images
use CoreImage for decoding/encoding images on osx/ios
fix gyp project
also allow underscores in token names
bump cocoa
use more modern libpng version instead of the system-provided one and fix compile errors
Merge branch 'master' into platform-image

Conflicts:
	gyp/install.gypi
use -lpthread instead of -pthread
fix image y reversal
Merge branch 'master' into platform-image
bump cocoa bindings
Merge pull request #527 from mapbox/platform-image

Use platform-specific routines for decoding/encoding images