[1.2.0] Add monitoring recipe for Sensu integration

Welp:
* Adds a `monitoring` recipe which will generate a check per HAProxy backend
* Bumps version to 1.2.0

Currently missing the actual Sensu plugin because I haven't sent it upstream yet B-) could also just ship it in here but that sucks I suppose. Not sure if we'd want to put this recipe here -- I think it's acceptable despite being for a different utility, but open to why that is not so.