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
req.pipe(res);
    }).listen(4444, function () {
      axios.post('http://localhost:4444/',
        fs.createReadStream(__filename), {
        responseType: 'stream'
      }).then(function (res) {
        var stream = res.data;
        var string = '';
        stream.on('data', function (chunk) {
          string += chunk.toString('utf8');
        });
        stream.on('end', function () {
          test.equal(string, fs.readFileSync(__filename, 'utf8'));
          test.done();
        });
      });
    });
  },
  testBuffer: function(test) {
    var buf = new Buffer(1024); // 
    buf.fill('x');
    server = http.createServer(function (req, res) {
      test.equal(req.headers['content-length'], buf.length.toString());
      req.pipe(res);
    }).listen(4444, function () {
      axios.post('http://localhost:4444/',
        buf, {
        responseType: 'stream'
      }).then(function (res) {
        var stream = res.data;