Remove ClassGuesser as it is too early for one

ClassGuesser provides ability to use predefined
steps withtout the need to create FeatureContext.
There's not enough predefined magento steps to do
that just yet and also provided guesser is wrong.
Cleanup MagentoContext step definitions
Remove spec leftover from ClassGuesser
Remove BeforeScenarioListener

We decided that cache is part of application
and implementation layer, not the business logic,
so it doesn't make sense to clear this automatically.
There is still a step for that task though.
Remove unneded service definitions from container config
Empty registry after fixture clearing
Remove controller from copy/paste
BehatMage users will be able to also pull upcoming Behat minor version updates
Users will have loose PHP version constraint
Users are provided with a clear step by step guide to show them how to use BehatMage as intented by its developers
Users are provided with a clear step by step guide to show them how to use BehatMage as intented by its developers
Merge pull request #14 from MageTest/cleanup

Cleanup