Enhanced Feature: View port following

I have made a small improvement to the viewport following feature.

I got frustrated with the whole map moving up and down every time I jumped so I decided to "disable" the viewport following when the sprite jumps.

The followed sprite will still be able to move vertically through the map. (ex. when the sprite jumps and lands on a collision platform that is higher than the starting platform, the viewport will follow.) 

Usage:
stage.add("viewport").follow(player,{ x: true, y: false },true);