Don't import student RSVPs for waitlisted students

Delete imported RSVPs that were created for waitlisted students.
Upgrade shoulda-matchers to 2.0.0

Fixes #133
user can rsvp from the event detail page feature

updated event detail page so that it doesn't break tests
Merge branch 'user-rsvp-event-detail-page' of https://github.com/treble37/bridge_troll into treble37-user-rsvp-event-detail-page
Students can RSVP from Index or Event Detail page

Students are asked their OS and 'Class Level'

Volunteers and Students are both now asked their 'Job Details'

This feature can be turned off with ENV['DISABLE_STUDENT_RSVP']
Show RSVP'd students on the event show page

Add some students to seeded event
Render session starts_at and ends_at in time zone always
Add simple_form to clean up radio button logic

Fix appearance of radio buttons on student RSVP when OS validation error occurs