Add functions: copy image, transform color space, sepia. Const color space

[antkowiakit]

const color space list,
Add functions:

• copy image
• transform color space
• sepia

[sergeyfedotov]

You should edit the .moon files and recompile project with a command line tool http://moonscript.org/reference/command_line.html#command-line-tools/moonc

[antkowiakit]

Fixed

[leafo]

Sorry a about the delay, reviewing this MR now. Two things:

• Don't add new top level library functions, having them as methods of Image is fine
• Every new method added to the image class needs a spec.

[jt55401]

@antkowiakit and @leafo - any chance you have time to finish this? I think we're having an issue that's related to colorspace, and I'd love to be able to transform colorspace in process.