Coloring

Covers https://github.com/KSHSK/WAVED/issues/77

This PR is not feature complete right now, but I wanted to get it out there while I work on the final features.

* Please note that this DOES NOT cover refresh for coloring (https://github.com/KSHSK/WAVED/issues/206) right now. This is in progress and will be included in this PR in a later commit.
* Please DO NOT test any coloring with actions. They do not work and will not work until the refresh works.
* Since we don't have any files that we can actually use for gradient coloring, I made one with state populations from Wikipedia. Download it here: https://www.dropbox.com/s/m1w2wj5txs1r0pi/statepops.csv

 A nice, non-blinding color scheme to test with this file is shown in the screenshot below.
![screen shot 2014-04-13 at 7 48 43 pm](https://cloud.githubusercontent.com/assets/3300970/2690832/642d40c4-c366-11e3-81d0-531469499376.png)