[WIP] Ipython animation

This is work in progress.  It's a very basic implementation to allow creation of animations from PyClaw output in the IPython notebook without a lot of code.  Indeed, all you have to do is something like

    claw = setup()
    claw.run()
    from clawpack.visclaw import ianimate
    ianimate.ianimate(claw)

Obviously there aren't a lot of options yet.  I included an optional plotdata argument, because ideally I'd like this function to be able to accept one and animate the plots that would usually come out of visclaw.  The complication is that the animator needs a handle to a line or an image (for instance) in order to call set_data at later frames.  I think it would be best to refactor frametools.plot_frame to return such a handle, but that looks like a substantial amount of work.