RSVP Working!!!

Got the RSVP to work by configuring both the applicaiton_controller,
user_controller, and registrations_controller to correctly update the
@user MongoDB model. Added the rsvp_confirmation and rsvp_count fields
and adjusted HTML in the authenticated.html.erb to show the RSVP option
if the user had not already committed their RSVP and to hide it if they
had done such.