Add Bluebird promises

[benjamingr]

Bluebird is a popular Promise library.

https://github.com/petkaantonov/bluebird

It is also the fastest implementation by quite a margin and the one with the best stack traces. It is very applicable in NodeJS.

Please consider adding it to your list of implementations.

[izidorome]

+1

[ForbesLindesay]

I've decided to remove the list of implementations (and redirect that to the list maintained by Promises/A+) instead, this site can just provide one single "polyfill"