Initial commit of Pingdom Agent.  Grabs Pingdom checks to pass along to other agents.

I use the memory hash to store the last Pingdom check and only create events if the status has changed from the previous check in.  I've been running this internally for the last couple days without any issue, and its been updating agents it sources perfectly.

I've provided real data from my Pingdom queries in the rspec, so all should be well.