Add Participant.find_by_card method.

Fetches JSON data from server acting as a proxy to the CMU ID card
SOAP service.
Change find_by_card method in participant model to accept full
card number and parse the substring we care about out.
Move card lookup details to a separate cmu card model.
Have Participant.find_by_card use this.
Can search for students that are not already participants by
calling cm_id_card.search directly.
Add create participant functionality (by card number or andrewid lookup)
Put 'Add New Participant' link on participants index.
Merge branch 'master' of https://github.com/sc0v/trailerapp