Transform module to ES5

[nikitosss]

Please transform the module into ES5.
Thank you

[sindresorhus]

This module mainly targets Node.js, not the browser. It's up to you to transpile it with Babel if you want to use it in the browser. You can find a more detailed explanation here: sindresorhus/ama#446

If you use Webpack, check out babel-engine-plugin, which transpiles only the dependencies that needs to be transpiled.