Add bower support

[EvHaus]

Can you please consider adding bower support?

[ForbesLindesay]

Considered it, not doing it. Use browserify + npm.

[edef1c]

@ForbesLindesay didn't we still maintain a prebuilt bundle somewhere? that'd do just fine for Bower afaik

[ForbesLindesay]

We have https://www.promisejs.org/polyfills/promise-6.0.0.js which is a prebuilt polyfill, but I'm not currently maintaining a universal module definition build, although a user who wants one can easily build such a thing using browserify index.js --standalone Promise > output.js