Update tests to not actually use MIME::Lite::send

This stops us actually sending emails in the tests (even if they are to
example.com) and resolves some difficult to reproduce forking issues that
cause "Tests out of sequence" failures because TAP output is being printed
twice.

See the failures here for some examples:
http://www.cpantesters.org/distro/C/Catalyst-Plugin-ErrorCatcher.html#Catalyst-Plugin-ErrorCatcher-0.0.8.14
README.mkdn -> 0.0.8.15