Update board.html

Just added "margin: -8px;" to the end of <div id='gameScreen' style='width:100%; height:100%;'>. This will remove the white boundary around the screen for Google Chrome users. I don't believe this will have any effect on different browsers.
Merge pull request #1 from Yaffy/patch-1

Update board.html
Merge branch 'develop' of github.com:TLsoku/Card-Game into develop