fixes and tests

this branch includes Alej0veras's PR ([pr 18](https://github.com/rwillmer/django-behave/pull/18), [pr 20](https://github.com/rwillmer/django-behave/pull/18)) and adamestein's PR ([pr 19](https://github.com/rwillmer/django-behave/pull/18).

Rolled back from `undefined_steps` to `undefined` in PR 18, which was not working for me. If this was needed for Alej0veras, we need to figure out why there is the difference (I'm guessing a difference be Behave version?) - I am on behave 1.2.3.

I have added a full example project and app. 

I have added a `tests.py` that currently runs 3 basic tests - that behave tests run, that `--failfast` fails before behave tests run, and that `--behave_tags` work. There are obviously quite a few more that can be added, but this is a start that can be hooked up to travis to make everything much easier.

Thanks for all your work on this!