implement Clock.takeback
always fix castles when importing FEN
Merge branch 'antichess' of git://github.com/Happy0/scalachess into antichess

* 'antichess' of git://github.com/Happy0/scalachess:
  Allowing promotion to king in binary format parser
  ditto
  Changing name of the variant to antichess
  Moving stalemate responsibility out to variant. Since in suicide chess, the winner is not the previous player, the variant also determines the winner
  Moved responsibility of generating the list of moves to Variant. Changed a couple of minor things as per code review.
  Adding antichess (kamikazee chess) variant
Merge pull request #1 from ornicar/antichess

merge upstream master