In my case I have a `http_proxy` env variable on my development computer which passes all traffic to my vpn, however this proxy would fail to work when hostname is `localhost`, therefore when I'm testing my application it always fails because I setup my server at localhost, I want a method to force axios receiving a `none` for proxy config, currently if `proxy` property is `null` or `undefined` it will use the `http_proxy` env
test/unit/adapters/http.js
var axios = require('../../../index');
var http = require('http');
var url = require('url');
var zlib = require('zlib');
var fs = require('fs');
var server, proxy;
module.exports = {
  tearDown: function (callback) {
    server.close();
    server = null;
    if (proxy) {
      proxy.close()
      proxy = null;
    }
    if (process.env.http_proxy) {
      delete process.env.http_proxy;
    }
    callback();
  },
  testTimeout: function (test) {
    server = http.createServer(function (req, res) {
      setTimeout(function () {
        res.end();
      }, 1000);
    }).listen(4444, function () {