Add Poltergeist driver
Merge pull request #137 from dharalanov/master

Add Poltergeist driver
Remove unused code

SessionInvitationMailer.spots_available was removed in 6f76450
Merge pull request #138 from pvcarrera/master

Remove unused code
some minor changes to README.md
Merge pull request #141 from steverob/readme-changes

some minor changes to README.md
handle waiting list
handle waiting list and reminders.
Merge pull request #142 from despo/add-waiting-list

Add waiting list
update gems
update FAQ.