Added support for colormaps to Hinton diagrams.
Added support for colormaps to Hinton diagrams.

This should help provide accessibility support, as the red/blue
colormap can be difficult to impossible to read for colorblind users.

qutip/qutip,zasdfgbnm/qutip,cgranade/qutip,anubhavvardhan/qutip,anubhavvardhan/qutip,cgranade/qutip,zasdfgbnm/qutip,qutip/qutip