colorbar / legend

[7yl4r]

It would be nice to have a colorbar or legend in the UI, but for now maybe we can put a colorbar and references in the readme

[MathewBiddle]

Added in commits:

• https://github.com/MathewBiddle/globe/commit/1f50dbb85e5a6ee6da47deeda38b53c660f714e9
• https://github.com/MathewBiddle/globe/commit/5fc6f66f6166489c96bec5e5e8f8ae6150f1e3e3
• https://github.com/MathewBiddle/globe/commit/0fb40291ee7555befc06eb4d6bd193eff6f21c80
• https://github.com/MathewBiddle/globe/commit/d11b902c71f466bc91d982c8cecd110f64eb8e93