Update InlineCommentSummary UI

Summary: Minor spring cleaning, improve the visual feel of the comments table, more consistent structure.

Test Plan:
Test multiple comments, long comments, short comments, and multiple lines.

{F282462}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: hach-que, Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11666