Adds StatHat monitoring

Fixes #5 

Adds StatHat monitoring for:
- mbc_user_event_birthday:consumeBirthdayQueue
- mbc_user_event_birthday:sendBirthdayEmails_MandrillSent
- mbc_user_event_birthday:sendBirthdayEmails_MandrillERROR_invalid
- mbc_user_event_birthday:sendBirthdayEmails_MandrillERROR_unknown