Add volunteers to section organizer page

Add section organizer section widget to style guide
and style it a bit
Remember how the secret_token was in github? Guh.
[#49528619] completed waitlisted students should see edit/cancel rsvp button
Merge branch 'student_waitlist_index' of https://github.com/sowjumn/bridge_troll into sowjumn-student_waitlist_index
Student RSVP functionality can be turned off on a per-event basis
Sort event_sessions by ends_at DESC
Add city to location displayed in event index
Add gravatars to event detail page
Provide known width percentages for upcoming events table
Focus on email field when sign-in modal shows up
Add dietary restriction field to RSVPs.
StudentSorter: Use jquery.event.drag instead of jqueryUI/sortable

Volunteers are draggable now too. Still doesn't save anywhere.
Add an attending table with logistic information.
Limit student view to organizers.
Fix students controller test to respect new visibility restrictions
Destroy user RSVPs when destroying a user
added class level pref for volunteers
Change `height` property for `#section-organizer`

to `min-height` so that long lists of students don't overflow the container.
Add horizontal spacing between s.
Merge branch 'volunteerlevels' of https://github.com/Dreyfuzz/bridge_troll into Dreyfuzz-volunteerlevels