Re-enables shirt options

Adds a missing function call so the shirt options now display when they
should.
Fix badge price display

Fixes the case where the badge price may go into the negatives when the
attendee encounters a validation error.
Make use of badge_cost

Replaces a bunch of extraneous cost with attendee.badge_cost, which
already did everything I needed it to. Derp.
Add badge number display

Adds the badge number and a disclaimer for attendees confirming their
registration.
Merge pull request #800 from magfest/fix_confirm_page

More confirm page fixes