Bug 1019672 Add steps: pip, setup.py and running unit tests.

@bitgeeky r? If everything looks ok to you, we can run it by Bob.
Actually, I just figured it out myself (thanks Google). Based on a blog post [1], I added an environment variable to the beginning of the pip command, so my full command line is:

`ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future pip install -r requirements/compiled.txt`

I think we should add a note to the readme to do this if that error is encountered.

[1] http://kaspermunck.github.io/2014/03/fixing-clang-error/