Addition of lineHeightBuffer, JSHint fixes

* Addition of this.lineHeightBuffer (PIXI.CanvasBuffer(300,150) to PIXI.Text instances
* Adjustment down of approximation of CSS line-height from 1.5 to 1.2 as per general usage (https://developer.mozilla.org/en-US/docs/Web/CSS/line-height)
* Various fixes of trailing whitespace from JSHint