Update README.md

Clarifies that this is an engineering effort.
!tck #12 Migrated TCK to plain Java

* In which we trade off less-DRY in order to be scala-version independent.
* TCK does not depend on Scala at all now.
* Added tests testing the TCK, if we properly delegate all tests from Processor -> {Producer, Subscriber}
* Made SBT run the TestNG test
* Made the "pending" tests (decided by returning null in the special create... methods) actualy visible as PENDING to testNG