Minor improvements to demo programs Stars and Stonehenge
Minor improvements to demo programs Stars and Stonehenge

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