Refactor run tests

- In development run `./run_tests.sh`
- `jenkins.sh` uses `./run_tests.sh`
- `.travis` uses `./run_tests.sh`

Simples!

This assumes that you're using virtualenvwrapper in development (or at least have your `WORKON_HOME` environment variable set). If you're not then you will need to be in a virtualenv before executing `./run_tests.sh`

This depends on #113