Move some test helper init.
Puts control of the input goroutine into the InputRunner, which saves some finicky
boilerplate and gives us a slightly better chance to recover from panics. Also adds
LogMessage method to PluginRunner for consistent output when there's not an error.
Fixes UdpInput hanging on shutdown.
Waitgroup is handled by the InputRunner, no longer needs to be passed in to the
Inputs.
Merge branch 'dev' into features/run-plugins

Conflicts:
	pipeline/mock_outputrunner_test.go
	testsupport/mock_net_conn.go
update mocks
Change filters and outputs to use `Run` instead of `Start` where the goroutine is
started and managed by the calling code in the Runner instead of within the plugin.
Also get rid of the separate InChan and MatchChan to simplify plugin implementation,
substituting w/ a `Deliver(pack *PipelinePack)` method on the runner that will wrap
the pack in a PipelineCapture and drop it on the input channel.
Slightly cleaner equivalent logic.
Merge pull request #48 from mozilla-services/features/run-plugins

Features/run plugins