Prepare for 1.6

  remove scatter
  update versions Fixes dc-js#278

fix dc-js#228

[dc-js#178] introduce clip padding

missing semicolon

missing semicolon

[dc-js#131] introduce filter handler

[dc-js#67] fix filtered listener interaction problem and updated api doc

move wiki.md

[dc-js#68] improve empty brush handling

tag 0.9 release