Email throttling

Emails will be throttled based on the `to` email address.
The throttling window and count can be configured from config.js
This relies on a new module called `redis-throttle`
Fixed jshint error in oae-emails/tests
#764 - email throttling - follow-up
Merge pull request #764 from simong/email-rate-limiting

Email throttling
Email throttling improvements

* Rate-limit using Redback
* Serialize sending emails so counts are accurate on a given when
  sending a batch of notifications
* Reduce number of buckets for better memory efficiency and count
  read performance
Reformat configuration object for email api init method
Merge pull request #765 from mrvisser/redback-throttle

Email throttling improvements
Added forceProfileUpdate to force update display names during CSV (re-)import
Default forceProfileUpdate to false
Stringify boolean value in rest util
Merge pull request #767 from nicolaasmatthijs/forceProfileUpdate

Added forceProfileUpdate to force update display names during CSV (re-)import
(Release 4.1.2) Bump version
(Release 4.1.2) Remove shrinkwrap
Fix email configuration when initializing API
Roll back 4.1.2 tag
Merge pull request #768 from mrvisser/email-config

Fix email configuration when initializing API
(Release 4.1.2) Bump version
(Release 4.1.2) Remove shrinkwrap