Add invite capability

[shamsq]

User should be able to select multiple invitees from their address book (social media sites?). When a user creates an event, all invitees should be notified of their invitation and presented with options to accept, decline or tentatively accept attendance to the event. Once an invitee selects an RSVP option, this will be tallied on the server, and event creator will be notified in almost real time.

[jancel]

Updated story to add a bit more requirements.