Pull stream from Promise

Convert a Promise into a pull stream source.

``
fromPromise(Promise [, Boolean ]) -> PullStream

fromPromise(Promise ) -> PullStream
fromPromise(Promise(Array) , true) -> PullStream
`

Call with true for the spread parameter and the promise will be expected
to resolve to an array and each item be pushed to the pull stream.

`js
var pull = require('pull-stream');
var formPromise = require('pull-from-promise');

pull(
fromPromise(Promise.resolve('something')),
pull.collect(function( err, array ){
console.log(array); // [ 'something' ]
})
);
`

`js
var pull = require('pull-stream');
var formPromise = require('pull-from-promise');

pull(
fromPromise(Promise.resolve([ 1, 2, 3 ]), true),
pull.collect(function( err, array ){
console.log(array); // [ 1, 2, 3 ]
})
);
``