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 string = '';
        stream.on('data', function (chunk) {
          string += chunk.toString('utf8');
        });
        stream.on('end', function () {
          test.equal(string, buf.toString());
          test.done();
        });
      });
    });
  },
  testHTTPProxy: function(test) {
    server = http.createServer(function(req, res) {
      res.setHeader('Content-Type', 'text/html; charset=UTF-8');
      res.end('12345');
    }).listen(4444, function() {
      proxy = http.createServer(function(request, response) {
        var parsed = url.parse(request.url);
        var opts = {
          host: parsed.hostname,
          port: parsed.port,
          path: parsed.path
        };
        http.get(opts, function(res) {
          var body = '';
          res.on('data', function(data) {
            body += data;
          });
          res.on('end', function() {
            response.setHeader('Content-Type', 'text/html; charset=UTF-8');