Promise.delay() does not produce long stack traces

[ben-page]

1. What version of bluebird is the issue happening on? 3.4.1

2. What platform and version? (For example Node.js 0.12 or Google Chrome 32) Node.js 4.7.1 on Windows x64 There is no call stack at all on newer version of Node. See No call stack with runaway promise warning #1181

3. Did this issue happen with earlier version of bluebird? Yes

Promise.resolve()
    .then(() => {
        Promise.delay(1000)
            .then(() => {
                console.log('inner');
            })
    })
    .then(() => {
        console.log('outer');
    });

Console

Warning: a promise was created in a handler but was not returned from it
    at processImmediate [as _immediateCallback] (timers.js:383:17)

outer
inner

[ben-page]

It looks like delay is missing a call to _captureStackTrace(). I added it in the PR.