added canvas.setImageSmoothing

fixes #330 . However this is not working on FF (see original issue)

Example test to run under !FF
```javascript
Crafty.init(600, 300);
Crafty.background('rgb(0,0,0)');
Crafty.viewport.scale(6);

Crafty.canvas.init();
Crafty.canvas.setImageSmoothing(false);

var ent = Crafty.e("2D, Canvas, Image")
	.image("squares.gif") // replace with image of your choice
	.bind("Draw", function(e) {});
```