brainless 0.8.4

Two fixes to the new brand.

• The social card keeps the whole name. The 0.8.3 card was cropped to 2:1 and lost
  the b of brainless. It is now the full banner, padded top and bottom with its own
  night-blue ground.
• Buzz agents keep their avatar. The installers set the kilim icon together with the
  display name. A Buzz profile update replaces the whole profile, so a reinstall that
  set only the name would have wiped the picture. BUZZ_AVATAR_URL points it elsewhere.