fixed vmin/vmax for VertexRGB
fixed vmin/vmax for VertexRGB

CVML/pycortex,gallantlab/pycortex,gallantlab/pycortex,smerdis/pycortex,CVML/pycortex,smerdis/pycortex,gallantlab/pycortex,CVML/pycortex,smerdis/pycortex,smerdis/pycortex,CVML/pycortex,gallantlab/pycortex,smerdis/pycortex,gallantlab/pycortex,CVML/pycortex