function SamplePlugin() {
		throw("SamplePlugin cannot be instantiated.");
	}
A sample TweenJS plugin. This plugin is purely for demonstration, and contains documentation and helpful tips on
building plugins.

It sets the y position of the target based on a sinusoidal function of its x position.

NOTE: The code for this class is heavily commented. Please look at it if you'd like to write a plugin.

A TweenJS plugin is simply an object that exposes two properties (id, priority), and three methods (init, step, and change).
Generally a plugin will also expose an <code>install</code> method as well, though this is not strictly necessary.
@class SamplePlugin
@constructor