How to use the appengingtesting framework

I've started to look at goon for my project.  Before I made a large number of changes (due to API changes), I wanted to make sure I was doing it right.  I read the comment about automated testing so wanted to help in that regard.

You'll have to [install appenginetesting](https://github.com/icub3d/appenginetesting#installation) but I think you'll find it's worth it when you get it up and running.  The install isn't actually difficult either.

There's still an error being created in appengine/datastore/datastore.go but I'm unsure of how to address it and it existed in the previous test environment.
datastore: internal error: server returned the wrong number of entities