Added more nagios checks

 * Monitor disk space on / on all nodes
 * Monitor redis connectivity on the cache nodes AND the proxy node
 * Monitor HAProxy service
 * Monitor HAProxy status (whether it's actually proxying)
Specifying how many processes we expect to be running for haproxy
Nagios - postfix mailq check

Added a check that monitors the size of the mail queue.
Note that this will **not** monitor the amount of *sent* emails, but
rather the amount of e-mails that are left pending in the queue.
Nagios check - Total mails sent
Added nagios to the performance environment
Added nagios config to the performance environment
Made puppet server part of the nagios misc group in the perf environment
Fixed up nagios in the staging environment
Merged master into proxy-nagios
Moved oaeservice::nagios::memory into common.json and alphabetized activity-cache classes


for production, performance and staging
Added the HAProxy::status check
Removed munin::master from the puppet classes
Merge pull request #80 from simong/proxy-nagios

Added more nagios checks