Add gradient to sidebar of comment cell.
Merge branch 'master' of https://github.com/opfo/app into feature/styling-comments-view

* 'master' of https://github.com/opfo/app:
  Add vote up/down selected state images.
  Change default background color to gray.
  Fix not settings the adjusted color.
  Add user display name to index string
  Refactor identifier to OPFModel and hash and isEqual methods
  Fix wrong background image being used.
Change sidebar's gradient saturation.
Merge branch 'feature/styling-comments-view'

* feature/styling-comments-view:
  Change sidebar's gradient saturation.
  Add gradient to sidebar of comment cell.