Remove Exceptional & re-factor

Have removed the dependency on exceptional.
Have re-factored to include extra error trapping when trying to send an
email.
Corrected a problem in proof.rb where it would only return one record
from the database at a time.
Added some additional validation code on email addresses and paths.
Will now retry the sending of a proof if the pdf doesn't exist when we
come to send the email.
Generally improved the service, but have removed all exception handling.