Added support for logging intermediary result before timeout

I added a feature we discussed on mailing list (the thread can be found here: https://groups.google.com/forum/#!topic/awaitility/AebI58y6VoU). Timeout is measured using Stopwatch class, like in Guava.

`IntermediaryResultHandlerTest` demonostrates and verifies the new feature.

All tests, yours and mine, went green. Let me know if you have suggestions for some other tests or corrections.

I used automated formatting of my IDE which differs slightly from yours.

Regards,
Maciej