Red test (in ERROR state!)
This test is an indication of unexpected bug (after its fixing it will switch to failure state)
Fixed bug in the test itself (I've forgotten about immutability of the Position class)
Disallowing castling if the king has moved.

This doesn't take into account castling permission for another side.
Extracted method for detecting possible castling destinations.
Keep correctly information about the fact if king has moved and thus right to castling is lost.
Covered 'permannent' condition of lost right to castle
Switched to really 'valid' moves in test (we don't have validation inside the move method)
Castling is not allowed after castling as well.
Merge pull request #88 from lrozenblyum/KingMovement

King movement