Useless files published to npm

[djorg83]

There are a lot of files published to npm with this package that are not needed to be downloaded and included in downstream applications.

The "files" attribute should be added to the package.json, or .npmignore should be updated.

package.json

{
  "files": [
    "lib"
  ],
}

.npmignore

src/
tests/
.babelrc
.eslintrc.js
.travis.yml
CHANGELOG.md
CONTRIBUTING.md