sets up a Raphael canvas in the div element below here (the div has an id =canvas_container)
creates an object with a given identifier, tetrimino, and uses the "path" method to draw out a
a tetris shape
uses the objects "attr" method to syle it with gradien stroke colour, stroke-width,
stroke-linejoin (set to "round"), and a rotation of 90 degrees for its starting orientation
It uses the shape's animate metod to rotate it 360 degrees over 2000 milliseconds
while reducing the stroke-width to 1,
and with an "animation easing" of "bounce" to end up with the bouncyness.
Finally it callback function, a call to a function to be executed when the calling
method finishes. This last function uses animate to rotate back to -90 degrees and set the width back to 10
but no easing after the called back function call.