Solve "cannot find module 'winstrap'" problem.

[hezedu]

I want to use var winstrap = require('winstrap'); directly.

But it will get an Error: Cannot find module 'winstrap'.

So I create this pull request.

Then we can use it like:

const express = require('express');
const winstrap = require('winstrap');
const path = require('path');
const app = express();
app.use('/winstrap_dist', path.join(winstrap, 'dist');

[msftclas]

All CLA requirements met.