Give organizers a list of volunteer emails

This will probably be replaced by a mailer eventually.
https://www.pivotaltracker.com/story/show/45012157
Merge branch 'master' of https://github.com/railsbridge/bridge_troll
Prevent non-organizers from seeing volunteer_email page

https://github.com/railsbridge/bridge_troll/pull/110
Fixing specs for volunteer_email

reconciles spec with rsvp validations
https://github.com/railsbridge/bridge_troll/pull/110
Volunteer_emails spec: sign in as admin

The app won't let you see the list of volunteer's emails unless
you're an admin.  As it should be.
https://www.pivotaltracker.com/story/show/45012157