Send an email to project owner when a project is backed.

* Also fix nav state on pledges.
* Use letter_opener gem to see fake email, but this doesn't work from behind the VM. Rails log is sufficient.
Add integration test for email. Fix a few other failing tests.

* Add SessionController nav state (this seems a horrible solution, must be a better way!)
* The factory for Project didn't have a User, this made the email tests fail.