Version 0.0.3: secondary alerter support

* Added support for secondary alerter via conf option
  `secondary_alerter`.  This is used when the primary alerter fails.

* Added support for logging alerts via `log_alerts` conf option.  When
  true, this will log all alerts in addition to following the normal
  alert process.
Merge branch 'master' of https://github.com/rpedde/python-alerter
Update changelog and setup.py for release.
Merge pull request #3 from willkelly/master

Version 0.0.3: secondary alerter support