Test rake command

[eknowlton]

Right now there are no tests for the rake command. We need a test for this.

[eknowlton]

It is now mock tested with #4

Hoping to maybe hook up a IMAP server with a expected state of emails, so that we can just run the rake task with an actual IMAP server. This may just be done in CircleCI but maybe we can do it locally.

Might want to look at https://github.com/y10k/rims

[eknowlton]

• test it relays messages
• Spin up rails server
• Mock task with STDIN for piped input
• Check for unprocessed email
• Check status code for success

and

• test it returns status code for failed
• Mock task with STDIN for piped input
• Check for unprocessed email
• Check status code for failure