Add options to image

[freeman-lab]

Lightning's image function should add some of the options from matplotlib.imshow. A couple that would be useful and straightforward (only requiring changes to the client, not the visualization itself) are:

• a cmap, which would be used to transform images using a colormap, and then show the resulting RGB image. if passed an RGB image directly, this option would be ignored.
• a clim that handles scaling when cmap is passed

It would also be nice to specify options for origin andinterpolation, but we'll need to first add options to the visualization itself (if possible).