add(haproxy.rb): Initial import of haproxy.rb from ck/agent-plugins

- I now owe lo@petalphile.com a beer if I ever meet him/her.
update(haproxy.rb): Update status strings for use with new agent

- Now compliant with
  http://docs.rackspace.com/cm/api/v1.0/cm-devguide/content/appendix-check-types-agent.html#section-ct-agent.plugin
fix(haproxy.rb): Remove redundant "status" from fail call
fix(haproxy.rb): "error" has meaning for old CK plugins. Don't use it.
fix(haproxy.rb): metric lines should start with "metric"
add(haproxy.rb): Add alarm examples and update header somewhat.
Merge pull request #14 from jayofdoom/jay/PortHaproxyCK

Port haproxy.rb to Rackspace Monitoring Agent Format