Add unittests for oonicli.

Allows to programatically run nettests.
Merge branch 'master' into feature/better_testing

* master:
  Update changelog for 1.0.0
  Fix bug in initializing of the test instance.
  Fix bug that leads to not showing the help if an option is not present.

Conflicts:
	ooni/tasks.py
Merge pull request #291 from TheTorProject/feature/better_testing

Add unittests for oonicli.