- Vault::Log.count emits messages in the new Librato-compatible l2met
  format.
- Vault::Log.time emits messages in the new Librato-compatible l2met
  format.
Merge pull request #15 from heroku/update-l2met-conventions

update-l2met-conventions

Vault::Log.count, Vault::Log.count_status and Vault::Log.time all emit messages in the new Librato-compatible l2met format.

The format is the one we've been recommended to use by Foundation and
is documented here:

https://github.com/ryandotsmith/l2met/wiki/Usage#logging-convention