Make hashtags at the end of bolded text render properly
Summary: Fixes T10096. The ** was being parsed as part of the hashtag, so **#asdf** interpreted #asdf** as a hashtag.
Test Plan: Unit test; bolded stuff with hashy contents.
Reviewed By: chad
Maniphest Tasks: T10096
Differential Revision: https://secure.phabricator.com/D15006