Added tests!

Could definitely use some more but I think this is a good start for #1.

I just went through the Backbone tests are reformatted any tests that referenced `fetch` or `create`. There were a few inconsistencies that I couldn't figure out which are marked by `TODO:` in `tests/main.js`. If anyone wants to look at those, that would be great. I also can come back to them with a fresh head.

Also I didn't test `getOrFetch` or `fetchById` yet but those are simpler in comparison.