/*
 * Return a new Imlib2::Gradient.
 *
 * Examples:
 *   # create a blue to green gradient
 *   grad = Imlib2::Gradient.new
 *   grad.add_color 0, Imlib2::Color::BLUE
 *   grad.add_color 100, Imlib2::Color::GREEN
 *   
 *   # create a red to yellow to black gradient
 *   colors = [ [0,   Imlib2::Color::RED    ], 
 *              [100, Imlib2::Color::YELLOW ],
 *              [200, Imlib2::Color::BLACK  ] ]
 *   grad = Imlib2::Gradient.new *colors
 *
 */
VALUE gradient_new(int argc, VALUE *argv, VALUE klass) {