On review requests, it can be difficult to discern new discussion from the old. This particularly pertains to finding new reviews and new comments on review requests with a lot of discussion.
This set of changes adds visual indicators/highlighting to all page entries and all comments that were posted since the user last visited the review request.
It essentially does this by adding reviews and comments to a CSS class if they were posted since the user last visited the review request. It then applies the visual indicators to the page using only LessCSS.

Checked if last_visited is passed down to the appropriate templates correctly.
Checked if the new-page-entry class and the new-comment class are applied when the conditional is true.
Checked if the page is updated with the correct styling when page-entries and comments are newer than last_visited (ie. indicators are added).
Checked if the visual indicators are removed when page-entries and comments are older than last_visited (ie. page refreshed on a page with page-entries/comments with the indicators).
Checked if the visual indicators are added and removed correctly in spite of any caching that might happen (ie. caching does not interfere with addition/removal).
Ran unit tests for checking if new-page-entry and new-comment are both added and removed correctly.