Change 'authors' to 'contributors' in package.json
Change 'authors' to 'contributors' in package.json

[The npm docs][npm-docs-contributors] specify that:
> The "author" is one person. "contributors" is an array of people. A
> "person" is an object with a "name" field and optionally "url" and
> "email"

We needed to reformat our package.json to correctly list a single author
and multiple contributors.

[npm-docs-contributors]: https://docs.npmjs.com/files/package.json

realestate-com-au/react-waypoint,NikolaIliev/react-waypoint,verbling/react-waypoint,plain-vanilla-games/react-waypoint,tobiasquinn/react-waypoint,brigade/react-waypoint,brigade/react-waypoint,TheNounProject/react-waypoint,nickclaw/react-waypoint