Use LSB functions in sentinel init script

Also fixes bind address config issue from #7
Add BIND_ADDRESS to init config file for Debian

Also only includes the REDIS_PASSWORD when it's set.
Update Travis tests for Sentinel
Bugfixes for Sentinel testing

 - Define monitor list in test_sentinel.yml playbook
 - Set Sentinel bind address in init config file appropriately
 - Don't insert Sentinel config options if they're False
Merge pull request #21 from DavidWittman/sentinel-tests

Sentinel tests