Robb/meeting registration

[ieatkimchi]

adds functionality to create attendee attached to a meeting and persist relationship validates presence of optional twitter handle and formats correctly

• removes all non chars except _ in handle for db
• @ is presented in UI with handle if handle exists
  • following pr will have func to select random attendee

[ieatkimchi]

• adds new route "/registration" can register for next meeting

• creates new attendee and redirects back to "/registration"

• can add more attendees to meeting

• throws UI error for bad email format

• throws UI error for invalid twitter handle

• accepts @ or multiple @ in twitter handle as optional and handles it in schema

• accepts twitter handle with no @

• adds attendee with no twitter handle

[ieatkimchi]

@Kartstig formatted and pushed.

[ieatkimchi]