Add colormap options to image transformations

[hannahker]

Similar to the implementation in #21, let's add at least one demonstration of a colormap transformation to the image display. This can be done using the hue-rotate() filter function: https://developer.mozilla.org/en-US/docs/Web/CSS/filter#functions

Note that we'll also have to apply sepia() so that it has an impact on the greyscale displayed image: https://stackoverflow.com/questions/23520159/apply-a-css-hue-rotate-filter-to-a-greyscale-image

Some calculation will also probably need to be done to figure out which rotation value corresponds to which color: https://stackoverflow.com/questions/29037023/how-to-calculate-required-hue-rotate-to-generate-specific-colour

[danton267]

addressed in #33

[hannahker]

Discussed further with LBL and decided that this isn't a priority at the moment.