Add esm support

[bgrins]

Found a simpler solution compared with #241 by using rollup directly, and moving all the cjs implementation (including tests which get duplicated) into a subdirectory

This also replaces a number of the current tools (grunt, docco, qunit) and will need some additional work to get testing running in CI.

Todo:

• [x] Set up github action
• [x] Set up pages on master, or merge to gh-pages
• [ ] Doc updates (readme, page)
• [x] Delete files (bower, docco, qunit, Gruntfile, travis.yml)

Follow ups

• [x] Remove things like mathRound = Math.round
• [ ] Export the utility functions directly
• [x] Publish a 1.5.0

[bgrins]

217

[bgrins]

https://github.com/bgrins/test-tinycolor-upgrade is looking good with a test deploy from this branch. Both CJS and ESM are working as expected