HubSpot/Singularity — pull request #333 by wsorenson (2014-11-13 22:38:44+00:00)
Title: rate limit mails

- rate limit is per mail type + request
- rate limit after a configurable # of mails in a given period
- lasts for a configurable amount of time
- notifies rate limit is in effect
- cleans up old metadata used to calculate rate limit