Mark this as a private npm package

See <https://www.npmjs.org/doc/json.html#private>.

Closes #303.
Fixed freqdec's Input Range Polyfill url
Merge pull request #304 from andreruffert/patch-1

Fixed freqdec's Input Range Polyfill url
Merge pull request #303 from mathiasbynens/private

Mark this as a private npm package
Add `rangeslider.js` as another polyfill

Close #305.