add new functions to Othello API
implement getId
implement observer functions
add move history class
add unmark method to NodeImpl
add swap copy function to NodeSwapper
OthelloImpl now uses MoveHistory to undo moves
add integration tests for undoing moves
add demonstration for undoing one move
notify observers on move and on game finished
fix bug where game did not notify ending game
test observer callbacks
move now throws exception in interface
remove debug output
Merge pull request #63 from mharrys/extend-api-othello

Extend API Othello