Packaging

These changes make it possible to install search using pip and a git url, which wasn't possible because the repository had no setup script.

    $ pip install git+https://github.com/potatolondon/search.git#egg=search

I've also added a wrapper for running tests. But it doesn't do anything about having the App Engine SDK installed. It would be nice at some point to have a test runner that sets up the SDK, and then configure a CI server somewhere.