Implement statsd hook

[cgilling]

It would be nice to have a hook that will output statistics to statsd. Some features that I think would be nice:

• namespace prefixing
• keep statistics per query (i.e. create a key for each query)

Possibly this could be implemented using the gokit statsd package, or maybe it would be best to implement generic support for a hook that uses the 3 basic types provided by gokit