UNTESTED Slight re-factoring, inline documentation, HSV interpolation support, and bugfix

Deleted node_modules (install coffee locally on your computer please.
Don't clutter up the repo…)

Various formatting changes around the document (comments, indentation,
line breaks)

There is now support for interpolating colours via HSV, with
conversions courtesy of Wikipedia's article.

Fixed an undocumented bug, wherein colours interpreted with
utils.convert_to_rgba would not be normalized to the 0-1 range, but
rather might stay in the 0-255 range.

Things are console.log'd only when Horizon.VERBOSE is turned on now.