Make Newman importable

[prakhar1989]

Right now if you have newman is installed in /node_modules you can't import as it is.

var newman = require('newman'); // doesnt work
var newman = require('src/Newman'); // works

I think it will be good if we add a index.js file in root folder exposing the Newman module so that its more intuitive to import.

Index.js

module.exports = require('./src/Newman');

This allows a simple import

var newman = require('newman');

Let me know if this makes sense and I can quickly push a fix. Will help us in writing a grunt plugin as well.

[viig99]

Makes sense