Use done() if available when resolving foreign thenables

[jsor]

This adds a check to Promise\resolve when resolving foreign Thenables if a done() method exists and uses this instead of then().

Ref #66

[jsor]

Ping @WyriHaximus @clue @cboden

[clue]

Not a big fan of this TBH.

Do any of the known "foreign thenables" actually implement the done() method?

I wonder if there's no way we can provide our done() logic even if the underlying foreign promise only offers a then()method?

[jsor]

@clue I haven't found a way to do so. The thrown exceptions are swallowed here.

The only way i know to break out here, would be to use an event loop and throw on nextTick.

[jsor]

Closing for too much duck-typing :D.
async-interop/promise (#76) might be a better option for interoperability.