Basic auth for backstopJS and Chromy

basic.json

{
  "username" : "foo",
  "password" : "bar",
}

onBefore.js

const basic = require('./basic.json')
const btoa = function (str) { return new Buffer(str).toString('base64') }

module.exports = function (chromy, scenario, vp) {
  require('./loadCookies')(chromy, scenario)
  const authHeader = btoa(basic.username + ':' + basic.password);
  chromy.userAgent(vp.userAgent);
  chromy.headers({
    'Authorization': 'Basic ' + authHeader
  } )
  chromy.ignoreCertificateErrors()
}