Improve test for make_printable
Add second test for output
Add test for make_human_move
Refactoring

I changed the name of 'make_human_move' to 'decide_human_move' because
it's only going to return the position to move to (and not actually call
board.place).
I also switched to using 'actual.should be(expected)' instead of using
'expect()' at Brian's suggestion.