fix supervisor test
travis build profile

* Log >= warnings to stderr
* Do not run tests in parallel
Log >= info to stderr
test: rule: wait for agent to come up

* Expose SystemTestBase methods to let
  TemporaryJobsTest to wait for the agent.

* Some SystemTestBase cleanup.
Merge pull request #3 from spotify/dano/travis

fix test + enable logging & use one test fork on travis-ci