Replace AsyncHandle with a proper Promise implementation

[dtao]

No description provided.

[FrozenCow]

So I did some searching:

I wasn't aware of this, but ES6 will get promises natively: http://www.html5rocks.com/en/tutorials/es6/promises/
It'll use the Promise/A+ standard. So it's a good idea to pick a library that can work as a drop-in for the native one, in Node as well as the browser.

Here are a few:
https://github.com/then/promise
https://github.com/cujojs/when
https://github.com/MaxMotovilov/node-promise
https://github.com/kriskowal/q

Most promising ones seem then/promise and cujojs/when. Both are made to work in browser as well as node, both seem to focus on compliance with Promise/A+, both seem fairly minimal and fast. It does seem cujojs has a longer history, so it might be safer to go for that. I haven't used any of them consciously, so I'm only looking at their descriptions at this time.

[dtao]

So I actually decided to get a bit crazy and implemented the Promises/A+ spec myself, in Lazy, which means Lazy.AsyncHandle is now a compliant promise (passes all 872 tests, phew!). My motivations were twofold:

1. I prefer to keep Lazy 100% free of dependencies (somewhat an arbitrary goal, I know—but it makes me feel good, anyway).
2. I thought it'd be fun to take a stab at implementing the spec.

This will be in the next release, which I'm now thinking will probably be 0.4.0 as there have been quite a few changes since 0.3.2.

[FrozenCow]

Nice! Looking forward to the release. 0.4.0 does indeed sound good for what it brings.

[hyzhak]

👍 for Promises/A+

[dtao]

Done in 0.4.0!