Add ability to define multiple test cases for same endpoint/response

Currently the test runner generates a test case per endpoint/response defined in the raml. It would be great to be able to define multiple test cases in situations where more thorough testing is desired to feed in slightly modified sample inputs via hooks.

There are several ways to approach this, but here's one thought I had to keep it minimalistic for the test author... We could add test instances during hooks file processing just by defining additional before hooks.

For example, if we have...
GET /endpoint -> 200

Then in the hooks file, to achieve multiple test executions we could specify additional hooks:
before GET /endpoint -> 200 ...
before GET /endpoint -> 200 arbitrary workflow 1 ...
before GET /endpoint -> 200 arbitrary workflow 2 ...

And when the hooks file is processed it could detect there are additional tests and add those into mocha.