New categories

@ndonald2 Yeah, this is intended to merge.
Fair, but I have strong feelings about macros. Macros make sense when you leverage their functionality for token replacement and expansion, or when you're condensing larger blocks of code into one line. To use them as a c-style method in order to replace a longer objc method is just an extra level of indirection, which tends to lead to cruftier code.

Also I would not call the category methods syntactic sugar in the same way I would call the macros syntactic sugar - they are performing value conversions in a much cleaner way than throwing arithmetic inline to the default `UIColor` methods (where you have to remember to divide by 255.0).

@mgorbach was asking because there used to be *only* macros. This is intended to replace that. But if the general consensus is that it's worth it for the smaller method signature, then I'm ok leaving the macros in. I just want to make sure we don't get in the habit of using macros to do things that plain methods do just fine.