Enable rich text for Review Bot comments.

Review Request #8762 — Created Feb. 17, 2017 and discarded — Latest diff uploaded

Information

ReviewBot
master

Reviewers

This change makes it so reviews posted through Review Bot's special review API
use rich text for the body-top and body-bottom, and allow rich text for the
comments (if passed in as True).

Modified the warning message that the worker uses if the number of comments has
been capped, and saw that it posted as rich text.