Add installing from source docs.
Add waitgroup to track WhisperRunners in the WhisperOutput so we can be
deterministic about knowing when things have shut down (fixes test failures that
started after go's new scheduler landed).
Merge branch 'dev' of github.com:mozilla-services/heka into dev
Add MGI internal channel data to the heka report.
Merge branch 'dev' into features/message_signing

Conflicts:
	testsupport/mock_net_conn.go