fixed update_marker and update_marker_size handlers to use marker size
fixed update_marker and update_marker_size handlers to use marker size

ChakriCherukuri/bqplot,dmadeka/bqplot,rmenegaux/bqplot,ChakriCherukuri/bqplot,SylvainCorlay/bqplot,SylvainCorlay/bqplot,dmadeka/bqplot,ChakriCherukuri/bqplot,rmenegaux/bqplot,bloomberg/bqplot,bloomberg/bqplot,bloomberg/bqplot,ssunkara1/bqplot,ssunkara1/bqplot,SylvainCorlay/bqplot