Coloured output

Hey!

I'm really enjoying this plugin but always felt the output could be coloured a little more to help pull out the important bits of information.

What this PR does is:

- add `.editorconfig` with your desired settings (4 spaces as tabs) and reindent runner.js accordingly (apologies, this makes the diff a little messy).
- Change `runner.js` so it logs a stringified object containing all the info on the tests and stack traces.
- use Chalk in `index.js` to colour output.

I have attached some screenshots of the output now, showing it for success and for failures.

![screen shot 2014-06-21 at 17 33 17](https://cloud.githubusercontent.com/assets/193238/3349422/a4cd5cea-f962-11e3-93b6-47b76bd32875.png)
![screen shot 2014-06-21 at 17 33 35](https://cloud.githubusercontent.com/assets/193238/3349423/a4ce623e-f962-11e3-915c-6a704ad9273e.png)
![screen shot 2014-06-21 at 17 33 49](https://cloud.githubusercontent.com/assets/193238/3349424/a4ceca3a-f962-11e3-88bd-1b63cac33ec3.png)

Let me know what you think!