Use of ES6 Proxy prevents running in IE

[Alamantus]

As mentioned in https://github.com/choojs/choo-devtools/issues/31, because the package delivered to NPM is not transpiled into standard JS, the package does not run on IE.

This Proxy polyfill does not work for this instance and "Due to the limitations of ES5, Proxies cannot be transpiled or polyfilled" (ref), so the best option would be to skip using it if it does not exist. I am willing to create the pull request, but I'm not sure what value to return for the main function if Polyfill doesn't exist. Would it just return the object?