Fix 9BTTT w/Pie bug spotted by Richard

Don't lose the currentBoard when the second player accepts the pie swap.  Just adds the additional rule...

(<= (next (currentBoard ?k ?l))
 (true (currentBoard ?k ?l))
 (does blue swap))
Merge pull request #20 from SteveDraper/master

Fix 9BTTT w/Pie bug spotted by Richard