Started on some e2e tests

I finally got around to set up automated testing for the library. I'm approaching it from the end-to-end perspective first (we should also add unit tests). 

These tests are designed to run the OJ build and server modes on test projects, expecting a certain output. Right now the tests make sure that: 

* Build files outputted in the correct path
* JS concatenation work
* The built in connect server works

These use cases cover a large portion of the functionality of the program, so it's a good first step towards good test coverage.

The idea is that we should add more example project, testing more complicated tasks: compiling angular templates, coffeescript, less, etc.

The e2e tests are written in bash using the bats testing framework. I also got them to run on travis-ci, which is really awesome because all PR's and branches will be annotated with test results. Travis is awesome!