Implement Runner type, remove Endpoint/Service

Discovery will no longer take place inside of bazooka.
We implement a Runner type as a substitute to Endpoint, to
register our service runners.
Remove Service & Endpoint from events
Remove Srv/Ep tests
Fix and test runner library
Runner unregister
Merge branch 'master' into feature/runner-no-ep
Merge pull request #89 from soundcloud/feature/runner-no-ep

Implement Runner type, remove Endpoint/Service