"Who Am I?" – log in with Personas

Pivotal Tracker ticket [#75075362](https://www.pivotaltracker.com/story/show/75075362), "As a City stakeholder, I want users of this system to have to log in before they can see any sensitive data."

Known TODOs:
- [x] make login page
- [ ] write tests
- [x] resolve merge conflicts with master
- [x] add login_required to the browse page
- [x] remove references to session['email']
- [x] prevent users from accessing pages besides '/' if they're not logged in
Correct, we're not doing anything with LDAP in this commit. Would you rather I set name to '' instead? My thought was that it should be something consistent so we can search for any users created this way. If LDAP doesn't come through, we'll need to determine a different way of setting or displaying usernames.