When the environment variable STACKDRIVER_LOGGING is set to true, send
request logs in a format that Stackdriver knows how to interpret. Also,
set the log level accordint to the status code. 4xx responses are logged
as warnings and 5xx responses are logged as errors.
This reverts commit fc2e043b20204e04f240814d4efc05762db7df96.
Had to revert this because req.route.path is not set until a matching
route has been hit, so it was always null inside res.end meaning
statsd data was never sent over.
This commit did not actually stop the memory leak so reverting it
has not short term repocusion