Adds basic testing and fixes includes with more than one argument

- Support for running `npm test` "out of the box"
- A few tests for fixing an issue that came up in the last release regarding live preview includes
- Brought back PhantomJS

Let me know how the directory structure for `/test/` looks, wasn't sure of the best way to lay it out. 

I'll probably merge this soon just to get the include bug fixed.