Event Show: Show gravatars of organizers
Signing in via the 'Sign in' link in the header always returns to the current page

Previously, if you visited a page that requires authentication (like /locations/1/edit),
then fooled around somewhere else on the site (without logging in), then finally signed
in via the modal, you would mysteriously land on /locations/1/edit.
Signing in via an OmniAuth provider leaves you on the page you were at.

(More or less -- if you sign in after having clicked "Volunteer!" on an event
page, it takes you to the RSVP form, same as if you'd typed in your
username and password).

Previously, it always sent you back to the home page.
Moves organizer-ish buttons to above Past Events table on events index
adds workshop requirements to top of event creation page
Merge branch 'features/70413054' of https://github.com/raebot/bridge_troll into raebot-features/70413054
Merge branch 'raebot-features/70413054'
Restore list-style-type: none as the default for ul tags

Remove unused scaffolds style sheet
Show waitlist positions on event show page
Organizer dashboard shows checkins breakdown by vols vs students

Checkin breakdown no longer includes waitlisted RSVPs in total

Fix some typos / troubles on the section arranger
Fix rounding ugliness on checkin counts