Meaningful exception classes on gpg failure

[mkamensky]

Hi,

I'm using the library in a rails application, and was getting NULL pointer exceptions when trying to deliver an email. Eventually traced it to this line:

mail-gpg/lib/mail/gpg/delivery_handler.rb

Line 19 in 1c77be4

raise $! if mail.raise_encryption_errors

but only a serious struggle. Would it be possible to wrap it in some more meaningful exception? Thanks!

[mkamensky]

Actually, I guess just not rescuing, or raising the same exception in place of $! would be sufficient