Comment UX

[corajr]

A few concerns:

• Replies currently appear above the comment they're responding to, which feels confusing.
• Flagging also seems to be a point of confusion, in part due to issue remove flaggable item on 3rd flag without reload #28.
• Display in chronological (rather than reverse chronological) order
• Enable threading
• Put "Report" next to flag and add an explanatory pop-over, as on the pins page
  • visual feedback that the flag has been added
  • maybe the text should be "Hide"
• Move add comment box to the bottom (and wrap in nicer bootstrap classes)