Can't make this to work with webcomponentsjs.

Hey mate

Thanks for providing this neat little component. I've used and extended it slightly to include caching / non-caching options - I will make it available shortly.

Just wanted to let you know that I've adjusted the way the reject-case is handled - according to the following guideline: http://making.change.org/post/69613524472/promises-and-error-handling

Hence, my error handling looks something like:

...
} else {
    var response = xhr.status + ': ' + xhr.responseText;
    reject(new Error(response));
}
...