Update bigbluebutton_rails with changes to the join process

The action 'auth' was removed and now only 'join' is used to join meetings.
Have yet to finish it in the gem and check if the permissions for 'join' are
ok in the app.
Update bigbluebutton_rails and few improvements in the join via mobile

refs #1247
Fix failing tests after last update of bigbluebutton_rails

After 85a110ccb96b973555d186351e57e77c8eb9b190