bug 891561: Support OS X signing in puppetagain. r=dustin
bug 891561: re-enable mac-signing4, now based on PuppetAgain manifests.
Bug 856123: fixes multiple issues in selftest-second-stage.py; r=dustin
Bug 891561: add nagios checks; r=bhearsum

For both Mac and Linux, although Linux is not currently monitored
(Bug 914139)
Bug 914627: install system git on Ubuntu; r=catlee