statsd is now supervised by upstart

We have encountered some hard to debug salt state dependencies so we
have decided to supervise statsd with upstart.
Merge pull request #38 from ministryofjustice/statsd-upstart

statsd is now supervised by upstart
Updated gem but previous commit broke the build

Previous few commits have not been tested but were merged in.
With those changes, salt no longer converges on the first run.
Fixed statsd upstart deficiencies.Updated Gemfile.Addded tests.

Original upstart file was missing few important bits - such as uid/gid
of spawned process. Furthermore statsd.sls state file was not starting
statsd process properly. Adding tests for statsd setup will prevent this
from going unnoticed.