Fix #45
Fix #50
add waitlist support and refactor ParticipantSignup api

Adds some basic waitlist support for issue #49. Still needs automated
(or manual) transition from waitlist to signup when space opens up in
the standard experiment signup pool
fix typo
update travis-ci and coveralls status

[skip ci]
fix ParticipantSignup.objects.with_attendance bug

Fixing copy-paste error and redirecting back to experiment session
signup when a session is full as there may be more sessions to select.
updating the subject pool test.

TODO: need to wire up waitlist into the front end, and allow for
waitlist confirmation as there may be other selectable sessions.
Refactoring update_round_configuration. Fix #42
Fixing cancel experiment session signup
Adding waitlisted signups to participant dashboard
Adding waitlist support to UI. Address Issue #49
Fixing autoselect experiment session bug. Fix #43
change contact form From: to message originator