GitHub IDs aren't unique
Update user email address with GitHub email

https://trello.com/c/d6uJF9Q6/192-collect-user-emails-when-they-authenticate
Don't fetch emails until migration has run
Revert "Don't fetch emails until migration has run"

This reverts commit e073c655a694e13adb670961af12c8157a458577.
move placeholder text into i18n