Add RWops class
Add custom RWops class which works with arbitrary container as a storage
Add tests for RWops
Add SDL_image2 support to cmake
Add Config.hh to record build-time settings
Options should only be used in standalone build
Allow to load texture fro file or via RWops
Update documentation for new features
Add demo for SDL_image support
Add custom RWops for use with constant containers
Merge branch 'image'
ContainerRWops are not assignable due to references; add noexecpt to move ctor
Mention template args