Changes from “Retention” to “User retention rate by month after sign-up”.
This should make it much clearer to people not familiar with retention charts
what it actually means.
* Add trending links
* Add overriding specific links trendability
* Add link type to preview cards and only trend articles
Change trends review notifications from being sent every 5 minutes to being sent every 2 hours
Change threshold from 5 unique accounts to 15 unique accounts
* Fix tests
Claire