Delegation regex should only match "Reviewed in ..." on it's own line.

[robertmonahon]

A PR description that included a line like "The previous version of this was reviewed in #-----" and then the author included code reviewers. Cody delegated to that other PR when I don't think that was the authors intention.

[aergonaut]

Should update the regex on https://github.com/aergonaut/cody/blob/master/app/models/pull_request.rb#L18