Log the reason into heka
Bug 1071244, 1071248 — Log WS errors + reason.

Previously to this commit, all the errors weren't actually getting logged to
heka, and their reason was never logged.
Remove useless var
Update the tests with the new hekaMetrics parameter
Merge pull request #215 from mozilla-services/bug1071248/websocket-heka-reason

Log the reason into heka