HOLD: Feedback faves and flags

This is the PR for the feedback faves and flags.

See: https://github.com/GigaOM/gigaom/milestones/Comment%20redesign%20v3:%20faves%20and%20flags
the query in `get_post_comment_states` is going to bind this in, so it's relatively safe, but it still feels like a good idea to sanitize this.