Always install extruder on travis
Always install extruder on travis

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