Update Joystick.js

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// Joystick.js
// Penelope iPhone Tutorial
//
// Joystick creates a movable joystick (via GUITexture) that 
// handles touch input, taps, and phases. Dead zones can control
// where the joystick input gets picked up and can be normalized.
//
// Optionally, you can enable the touchPad property from the editor
// to treat this Joystick as a TouchPad. A TouchPad allows the finger
// to touch down at any point and it tracks the movement relatively 
// without moving the graphic
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