Adding color property; setColor function

After some recent testing, I found that color was actually missing from the default_options (and will thus throw an error on construction).

Also found that getImageData returns an ImageData object NOT an Image and so it will not work with drawImage during Sprite's draw loop.

However, it will work with a canvas object, so the code has been changed, with the addition of a setColor function, to now use this. (setColor also allows for changing colors during runtime too.)