fix(promise): fix #891, sometimes NativePromise will not ready, and reduce zone.js size

[JiaLiPassion]

fix #891

1. sometimes NativePromise will not be fully ready when override global.Promise, we should add check about it.
2. now by default, typescript 2.3 will compile iterable and spread operator with new polyfill code and will make dist/zone.js bigger, and we don't really have to use iterable and spread, so we use simple loop to reduce the zone.js size.

[josephliccini]

@JiaLiPassion just so I understand this a little better, the core-js/es6/promise will:

Lazy load its prototype

can you elaborate a little more? Thanks!

[josephliccini]

it's => its (typo) :)

[JiaLiPassion]

thanks, I will update the comment.

[JiaLiPassion]

@josephliccini , sure, in core-js es6.promise, the initialization of ES6 Promise is

1. the Promise constructor was created, https://github.com/zloirock/core-js/blob/master/modules/es6.promise.js#L166
2. override global.Promise
   https://github.com/zloirock/core-js/blob/master/modules/es6.promise.js#L216
3. prepare Promise.resove static method.
   https://github.com/zloirock/core-js/blob/master/modules/es6.promise.js#L222

So this will cause the error.

[josephliccini]

Got it. Thank you!!