As a user, I want to be able to comment on other reviews, so that I can express more precisely if I agree or not with a review.

[jmcfig]

Acceptance Test

Scenario: User wants to comment on a review
  Given the user is logged in and viewing a review
  When the user selects the "Comment" button
  And the user writes their comment
  And the user submits their comment
  Then the comment should be displayed underneath the review
  And the user should receive a notification if someone replies to their comment