Fixed bug with the game not removing newly invalid available moves

When a piece was placed, all adjacent available moves would remain, even
though they would now be invalid. This has been fixed

Worked on #2, #3

    modified:   blockus.js
Work on calculating score and game finishing

Now player's have a score that is properly calculated. As well, added some
code to make it so the game ends.

Fixed #4
Worked on #2, #3

	modified:   blockus.js