Piper/tox for testing

### What is the problem / feature ?

This project was using my old pattern for running tests which does not benefit from some of the new stuff I've been doing.

### How did it get fixed / implemented ?

- Changed over to using [`pytest`](http://pytest.org/latest/) as our test runner.
- Changed over to using [`tox`](http://tox.readthedocs.org/en/latest/config.html) as our test harness
- Changed over to using [`flake8`](http://flake8.readthedocs.org/en/2.2.3/) as our code linter

### How can someone test / see it ?

Look at the travis test runs, or run the tests as noted in the README

*Here is a cute animal picture for your troubles...*

![turtle-coats](https://cloud.githubusercontent.com/assets/824194/4508993/cd1042a8-4b1a-11e4-9ae8-981be3457c25.jpg)