Mocking

[Lewiscowles1986]

I noticed these docs miss completely mocking the API & testing.

Due to the import / require time setup a lot of the examples give, this made me scratch my head a bit when using proxyquire to patch pg module import.

I've managed to get some bits working and wondered if it was worth documenting, or if the project goals require the standing up of a network service (postgres) when testing this module.

Either way it would be nice to get some docs and as I'm having a play at the moment, I wanted to know if you'd be open to a PR