refactor tests to use FactoryBoy for easier maintainance

[jurecuhalev]

Factory boy: http://factoryboy.readthedocs.org/en/latest/
Some slides: http://slides.xelnor.net/2012/pyconfr/factory_boy/

[sparkica]

Looks cool 👍

[goranche]

sheesh, the slides are hypersensitive (useless on a MBP with the trackpad)

[jurecuhalev]

I've created basic implementation of FactoryBoy and cleaned up two tests.

A lot of tests in test_events_processors rely on order of tests so I would like to look at those in a separate pull request.

If you feel this is enough of a change, I'll make a PR, otherwise I can further refactor tests.