Voting (Upvoting/Downvoting)

This pull request addresses upvoting/downvoting. (ID #70066648) 

Changes made:
- Ability to upvote/downvote or to undo vote
- Changed arrows + different colors when upvoting/downvoting (change as see fit :smile: )
- Comment list sorts by upvotes on refresh

Bonus:
Fixed 'characters remaining' (ID #70812826)

Please let me know of any implementation or high-level questions. :hearts: