Hi,

I'm using axios v0.17.0 with HEAD method like this:

`axios.head('http://example.com'); `

(let's suppose http://example.com is set to redirect 301 to http://www.example.com)

For some reason Request method will change on the first redirect to GET instead of keeping HEAD all the way down. This will read in logs like this:

```
example.com:80 10.0.0.1 - - "HEAD / HTTP/1.1" 301 237 "-" "axios/0.17.0"
example.com:80 10.0.0.1 - - "GET / HTTP/1.1" 200 246 "-" "axios/0.17.0"
```

instead of this:

```
example.com:80 10.0.0.1 - - "HEAD / HTTP/1.1" 301 237 "-" "axios/0.17.0"
example.com:80 10.0.0.1 - - "HEAD / HTTP/1.1" 200 246 "-" "axios/0.17.0"
```

When I do the test in Firefox it keeps original request method (HEAD) all the way down.

Any idea why is this?

Thanks,
Milos

test/unit/adapters/http.js
server = http.createServer(function (req, res) {
      res.setHeader('Location', '/foo');
      res.statusCode = 302;
      res.end();
    }).listen(4444, function () {
      axios.get('http://localhost:4444/', {
        maxRedirects: 0,
        validateStatus: function () {
          return true;
        }
      }).then(function (res) {
        assert.equal(res.status, 302);
        assert.equal(res.headers['location'], '/foo');
        done();
      });
    });
  });
  it('should support max redirects', function (done) {
    var i = 1;
    server = http.createServer(function (req, res) {
      res.setHeader('Location', '/' + i);
      res.statusCode = 302;
      res.end();
      i++;
    }).listen(4444, function () {
      axios.get('http://localhost:4444/', {
        maxRedirects: 3
      }).catch(function (error) {
        done();
      });