Polygon.contains returns true for points to the left of the polygon

[vilcans]

Test case:

        var game = new Phaser.Game(600, 400);
        var poly = new Phaser.Polygon(
            50, 0,
            100, 0,
            100, 50,
            50, 50
        );
        var contains = poly.contains(40, 25);
        console.log('Contains?', contains, '(should be false)');

Some optimization gone wrong maybe when porting PIXI.Polygon maybe?

Anyway, a simple fix.

[photonstorm]

I can't merge your PR (wrong branch, wrong files - see contributors guide), but have merged the fix locally anyway, so no worries 👍