Get feedback page into good enough shape to deploy

This commit gets our feedback page kicked into shape:

- Replace the old Twiter icon in the SVG with a hammer/pick icon
  (to be used for the Enhancements button)

- Add 'Community' section encouraging people to join us in QA
- Add mascot picture to liven-up the message

- Temporarily shelve the generic Feedback section as we don't have a
  mailing list, feedback form, or any other related infra set up yet.

- Tweak some layout and content via CSS