bump version to v0.5.1

v0.5.0 does not work and should not be used
Fix fail-fast behavior

* Actually wake the main thread in case of an exception in a reporter
* Properly cleanup after Zookeeper to avoid possible infinite sched_yield loop
  on exit
bump version to v0.5.2
Get a spec test for the example services

This checks that we can actually construct sane objects with the JSON
examples, which gives us some confidence that the examples are still
valid and we didn't forget to update them :)
Add a first initial rough cut of etcd reporter.

No real tests that this works yet, but it should be basically there..
Add documentation