function Rectangle(width, // This is the width 
                  height // This is the height
                  ){
   if (width){
      this.width = width;
      if (height){
	 this.height = height;
      }
   }
}
Create a new Rectangle instance. 
@class A basic rectangle class, inherits from Shape.
This class could be considered a concrete implementation class
@constructor
@param {int} width The optional width for this Rectangle
@param {int} height Thie optional height for this Rectangle
@author Gabriel Reid
@see Shape is the base class for this
@augments Shape
@hilited