Update README formatting
Add ability to delete a registration, and also for an administrator to 'undelete' the registration
Move the 'delete' link for registrations to be part of the 'edit' page
Closes #12. Prevent user from deleting a registrant which has payments associated
Closes #4. Update the feedback page to include the user's e-mail and registration name, if available
Change to use 'unscoped' instead of a named scope
Only allow undelete from admins