Tristan/haproxy

- Update Events labels:
before
![screen shot 2014-05-06 at 6 25 42 pm](https://cloud.githubusercontent.com/assets/1532259/2903439/10848cc8-d5f1-11e3-97f1-b8aa0415fd1e.png)
after
![screen shot 2014-05-07 at 10 09 16 am](https://cloud.githubusercontent.com/assets/1532259/2903452/33f6cffe-d5f1-11e3-9f5e-62bf0a1c4371.png)
(detail per svname, including aggregates)

- Update metrics:
  + improve performance
  + Optional count_per_status per svname
![screen shot 2014-05-06 at 6 26 15 pm](https://cloud.githubusercontent.com/assets/1532259/2903490/a77e537a-d5f1-11e3-831b-5ca96a1d9737.png)
Other tags are host, service, status, service_name
  + Leave metrics unchanged
  have both haproxy.backend and haproxy.frontend, with tags host, service, type, instance_url and backend