Issue #34: Use the Sensu check output as the OpsGenie alert descripti…

[Castaglia]

…on field.

Pull Request Checklist

Is this in reference to an existing issue?

General

• [ ] Update Changelog following the conventions laid out here

• [x] Update README with any necessary configuration snippets

• [ ] Binstubs are created if needed

• [x] RuboCop passes

• [x] Existing tests pass

Purpose

Known Compatibility Issues

[majormoses]

released: https://rubygems.org/gems/sensu-plugins-opsgenie/versions/4.2.0

[Castaglia]

Thanks!