Remove SpiffyTest dependency

Hi Spiffy,

This is my first step of the cleaning work (I've starting to clean Guards by reading carefully the whole code). I've been unable to run the tests, the problem was always Spiffy-Test, for some strange autoloading issues I couldn't debug.

So I simply get rid of it. I also:

- Made the Bootstrap.php class better and handling more cases (it mimics what we do in all Doctrine ZF2 module).
- I've renamed "test" to "tests" as most modules use this (and it makes more sense, there is no one test :D). I can revert this back if you don't like it.
- I've changed all mock from ORM entity manager to an ObjectManager. This module should not rely on ORM I think.