Adding Spock testing framework with sample test

spockframework configuration (712d5c16fbdb3ba6bf5de028cfdabaf284be9e9f and a69201bf5bbd1c6da2d3b823954515285727e877) together with sample tests:

* Spock 70b7b65de5efca26a345fd0dc52f76a87718fb85
* jUnit 6d924d0 (testing exactly the same thing as the Spock specification).

So as planned: framework + sample implementation.

I've also included few README words.