rtt_ros_integration: stabilization and release

[konradb3]

Many serious improvements came into rtt_ros_integration since Groovy. As we have stable release of Hydro right now. I think that we should consider to start working on the stable API and releasing whole toolchain into Hydro. Having the binary packages will provide us with mach broader adaptation of new feature and more testing/feedback.

[jbohren]

@meyerj @smits @psoetens

I've started to create a bunch of unit tests for the various packages. You can see them running here:
https://travis-ci.org/jhu-lcsr-forks/rtt_ros_integration/builds/12256382

Additionally there are some examples which I'd like to copy/migrate over to unit tests, shown here:
https://github.com/jhu-lcsr/rtt_ros_examples

I've also created a "Hydro Release" milestone in this repo. There are a lot of API breakages, and part of the release is going to require cataloging them along with a migration guide.