Refactoring and adding colour schemes.

They don't have a huge amount to offer right now, but should
hopefully be able to introduce a couple more when there's
more metrics to compare.

* "pastel" is just more of the same.
* "highlights" will colour `node_modules` folders green and `lib`
  folders orange, so it's easier to pick out what's specific to
  different modules (#4).
0.2.0