Add share to social button

[jimbobbennett]

Once scoring is in place, we should add an option to share this to social such as Twitter. This would be enabled via a button on the menu after you have ended at least one game.

This should auto populate a tweet with the users score, and details about the game, such as:

I scored 12 points whilst playing Cube Flyer as part of the @\MSFTReactor open source bootcamp

[runewake2]

Removing tagged user from the main issue.