Events: fix constant casing, Quit and Keyboard event types
Event: add vim folds for event structs
Sufrace: add ToTexture() and Free()
Renderer: add CopyTexture(), Clear(), Present()
Add image.go utility function for loading image
Add some TODOs for future work
image: remove double pointer
Clean up sdl.go
Merge branch 'master' of https://github.com/adam000/Go-SDL2 into init
A/C: add Google Inc./Ross Light
Merge pull request #5 from zombiezen/init

Clean up sdl.go
Merge pull request #4 from adam000/basic-rendering

Basic rendering code / Event improvements