[WIP] Unit Testing

**Work in Progress**

Experimenting with unit testing for the core library using [Mocha](https://github.com/visionmedia/mocha) and [jsdom](https://github.com/tmpvar/jsdom). Before running the suites we setup a jsdom environment and use it to load both d3 and epoch.

@bontibon - What do you think about this approach? Since unit testing is going to be limited to core functionality of the graphs and doesn't touch rendering, I am of the impression that this will work really well.