Fix gameLost bug

I wasn't sure whether this was an intended "Fix me!" feature or not, but currently the gameLost function is guaranteed to return True for basically every circumstance except one - I uncover all of the mines! This is probably not intended.

Instead, gameLost should return True if cc is Uncovered rather than Covered - this implies that a mine has been uncovered. Otherwise, it returns True if there are any mines that haven't been clicked on!