Add documentation for sprite
Add more documentation to display classes
Use the triple slash /// comments according to the Dart Style Guide
Merge pull request #158 from marcojakob/display-documentation

More display classes documentation
Update getting_started.md
Added ChromaKeyFilter

Kudos to @sebgeelen for the implementation.
Added Video implementation

Kudos to @sebgeelen for the initial implementation which was slightly
changed by me.
Update AUTHORS.md

Added Sébastien to the authors
Update AUTHORS.md
Fixed render loop
Changed name of constructor

It is very unlikely that someone used this constructor, so it's a minor
breaking change.
small improvements on video implementation in stageXL
getters  / setters
Merge pull request #163 from sebgeelen/video-improvements

Video implementation improvements
More work on the video implementation.
Document the video size hack in RenderTexture
Make the video constrcutor private
fix setters in VideoObject
More useful event streams in video
Expose BitmapFilterProgram publically to allow external extend