[#576] Fix particle min/max rotation and scale

- Created a new Number.prototype.randomFloat() method, since Number.prototype.random() returns an integer
- Fixed a bug with the random number generators overflowing the requested range, which goes back to the very first commit: https://github.com/melonjs/melonJS/commit/5f45e8e021a83280d7e35d7eabe82c03f865b31e#diff-be73193a7de1c86c1903f5cf92321d2aR103
Use double-inversion shortcut instead of Math.floor() (saves about 40 bytes)

* Old:
    Original: 835550 bytes.
    Minified: 224771 bytes.

* New:
    Original: 835510 bytes.
    Minified: 224731 bytes.
Replace Math.round with double-inversion + 0.5 (saves about 50 bytes)

* Old:
    Original: 835510 bytes.
    Minified: 224731 bytes.

* New:
    Original: 835471 bytes.
    Minified: 224688 bytes.