Merge pull request #41 from gwenzek/master

Finished and tested Drawable, removed draw methods from Canvas
corrected bug in overlay 

the overlay method wasn't iterating on the correct range.
Merge pull request #42 from gwenzek/patch-1

corrected bug in overlay
compilable, support for composite in canvas
Merge remote-tracking branch 'origin' into compilable
ColorModel
added greyscale color model
converted bicubic scaling from java to scala
added benchmark for the new scaling method
removed nested for loops
cleaner version of ResampleOpScala
Reformatted and moved new scaling implementation to scrimage package
Added scaliform to tidy code
Ran scaliform across the codebase
#49 improved speed of new sampling
Deprecated mutable image - lets push towards immutability and then add a better mutable abstraction once we've finished other work.
Deprecated mutable image - lets push towards immutability and then add a better mutable abstraction once we've finished other work.
more scaling filters, comments in Raster and ColorModel
added BytesColorModel (that uses Array[Byte] as pixel)
Added BytesARGBRaster