add scikit-learn to requirements.txt
add scikit-learn to requirements.txt

minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails