* master: (26 commits)
  Fix output quoting.
  Rework the README to allow the examples to be validated.
  New build
  Fix rollup config
  Switch from rollup-plugin-commonjs to @rollup/plugin-commonjs
  Replace uglify-js with rollup-plugin-terser, update rollup, simplify build setup
  Test on more node.js versions, lint and build on 14.
  Avoid no-prototype-builtins error
  eslint --fix . && prettier --write '**/*.js'
  Replace jshint with eslint
  prettier --write '**/*.{js,md}'
  Add prettier setup
  Try building on node.js 12 always, and only run the tests on the Travis-provided one
  Rename travis script to ci
  Drop package-lock.json, disable save-exact in .npmrc
  Bump lodash from 4.17.11 to 4.17.19
  Make npm build script possible to run on windows. refs #42 (comment)
  3.1.0
  Add luminance, contrast and darkness values
  Update author's email
  ...