Added moreland color maps

Created by: ctessum

These palettes/color maps supplement the ones that are currently available in that they are designed for pseudocoloring continuous variable (the brewer palettes are designed more for categorical variables) and they follow what I understand to be best practices for doing so, which the rainbow palette (although popular) does not.

Please take a look and let me know what you think!

This is related to issues #304 and #17 (closed).