Revert "Disable opsgenie clearing support for now"

This reverts commit 73ab8bbfee57311d88e5f8586bf00dc75a8c14e8.
First pass at opsgenie clearing
Delete auth and settings from opsgenie payload
Fix tests
Try and fix error
Merge pull request #82 from librato/opsgenie-clearing

Opsgenie clearing
Version bump to 2.25.0
Regenerate gemspec for version 2.25.0
Merge branch 'master' into victorops