Provide failing test case for king moves [ci skip]

Failing test case for the bug that @BiviaBen explains in #16

The following test case fails in master and passes in the branch BPC/benevolent-king-fix

Ignore travis-ci for master based PRs. Use phpunit tests/ChessGameTest to test.

Notice that testKingValidMovesMakingMoves is the test that fails. TestKingValidMovesWithMoveSAN passes.

//cc @jseverson @lackovic10