Add a global Promise polyfill. (#1344)
Add a global Promise polyfill. (#1344)

* Add a global Promise polyfill.
This is because Webpack2 depends on it.

* Change the polyfill location.

flybayer/next.js,JeromeFitz/next.js,callumlocke/next.js,zeit/next.js,flybayer/next.js,arunoda/next.js,nahue/next.js,BlancheXu/test,BlancheXu/test,azukaru/next.js,zeit/next.js,azukaru/next.js,BlancheXu/test,JeromeFitz/next.js,flybayer/next.js,azukaru/next.js,JeromeFitz/next.js,flybayer/next.js,nelak/next.js,kevmannn/next.js,kpdecker/next.js,JeromeFitz/next.js,zeit/next.js,azukaru/next.js,giacomorebonato/next.js,dizlexik/next.js