Added mouse events  (scene.waitfor, but not scene.pause).
Added mouse events  (scene.waitfor, but not scene.pause).

BruceSherwood/vpython-jupyter,BruceSherwood/vpython-jupyter,sspickle/vpython-jupyter,mwcraig/vpython-jupyter,BruceSherwood/vpython-jupyter,BruceSherwood/vpython-jupyter,mwcraig/vpython-jupyter,mwcraig/vpython-jupyter,mwcraig/vpython-jupyter,sspickle/vpython-jupyter