Removed karma and replaced with testem

I watched your video and you mentioned that you haven't done much on the testing front with Karma and this project. I replaced Karma with Testem, which I find much easier to use, less code and better reporting.

Please feel free to reject this PR. Here's a screenshot of me running the tests in a bunch of browsers:

![screen shot 2013-11-08 at 9 15 38 am](https://f.cloud.github.com/assets/12481/1501788/13e31c1a-4891-11e3-8ebc-e798a8b5465e.png)