* Change the background of bucket bar.
* Change margins, line height, font size, default state colour and hover state colour
  for different elements in the annotation card and the replies thread.

Trello cards:
https://trello.com/c/aXCXxzx2/327-update-the-visual-design-of-the-annotation-cards
https://trello.com/b/o2ungX1n/current-sprint