Add Enhancer for using Radium with ES6 classes

[ianobermiller]

I'm not really sure about the naming conventions, but this is a "higher order component". I've also played around with the idea of calling it a Decorator, since it can be used as-is as an ES7 decorator (https://github.com/wycats/javascript-decorators). We might also consider exposing wrapUtils (to satisfy cases like #123), although I'm not sure it is worth expanding the API surface.

Fixes #122.

[alexlande]

Finally played around with this and love it. Feels much nicer than the wrap method. Sorry about the merge conflict I introduced with the keyframes thing.

[ianobermiller]

How about naming? @colinmegill any comments here?

Some options:

• Enhancer
• Decorator
• Wrapper (tad confusing since we have wrap, but also maybe consistent?)
• HigherOrderComponent (far too wordy)

[coveralls]

Coverage decreased (-0.82%) to 42.75% when pulling 7a204a2 on es6-class-enhancer into ea96cfa on master.

[ianobermiller]

I'll add more tests for Enhancer once we have babel compilation support; it is hard to do stuff with classes without the class syntax :)

[coveralls]

Coverage increased (+56.43%) to 100.0% when pulling 4386311 on es6-class-enhancer into ea96cfa on master.

[ianobermiller]

I'll merge this now, and we can change the name afterward if we so desire.

[alexlande]

Posthumous comment: I like Enhancer. Lines up with a lot of the other higher order component discussions I've seen. Decorator implies that it is specifically an ES7 decorator, which would be confusing. Wrapper is too similar to wrap. HigherOrderComponent is indeed too long.