Work in progress: import autorestart into dogstatsd

Move AgentSupervisor to Daemon.
Plus a number of other pylint fixes.
Merge branch 'master' into dogstatsd-autorestart
Merge branch 'master' into dogstatsd-autorestart
Initial tests for autorestart
Merge branch 'master' into dogstatsd-autorestart
Add `make lint`
Move lint task to Rakefile :unamused:
pylint is now required to develop dd-agent
Indentation error
Completely terminate dogstatsd when autorestart is enabled
Do not hard-code parent class in Dogstatsd.stop()
Remove extraneous imports
Fix AgentSupervisor when watchdog kills child process
Update Daemon stop to kill process group
Don't autorestart dogstatsd unless specified.
Correctly stop non-autorestarted Daemons and update Red Hat init.d stop
Merge pull request #624 from DataDog/dogstatsd-autorestart

Dogstatsd autorestart, ready for kitchen testing before release.