add ipywidgets package, as requested by Ivica Nakić
add ipywidgets package, as requested by Ivica Nakić

tscholl2/smc,DrXyzzy/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,sagemathinc/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,tscholl2/smc