Feature/password reset broken

I think this might solve: https://www.pivotaltracker.com/story/show/77979268

The problem with the reset is when you tried to reset your password on staging, the staging app sent an email which in turn redirected you with a unique token to the *production* app (which knows nothing about the staging token).

This change ensures that links in emails sent from staging direct you back to the staging app.

**This code has special deployment instructions for staging** (you don't have to do anything special for production):

Once deployed to staging, run:
`heroku config:set RAILS_ENV=staging --remote staging`

And remember to set SECRET_KEY_BASE in your local .env. Take a peak at .env-template if you need a hint.

I don't believe anything special is needed for jenkins to run this code...