I have axios@0.15.2

If this HTML is run, some requests will be cancelled by Chrome:

    <html>
    <head>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.15.2/axios.js"></script>
    </head>
        <script>
        var promises = [];
        window.onload = function() {
            for (var i = 0; i < 4; i++) {
                var promise = axios.get('some url which causes ERR_CONNECTION_CLOSED');
                promises.push(promise);
            }
        }
       </script>
    </html>

![Cancelled](https://cloud.githubusercontent.com/assets/4506837/20349972/9123cef0-ac2e-11e6-93db-0ec66f205382.png)

But promises which turned into cancelled request won't be fulfilled:

![notfulfilled](https://cloud.githubusercontent.com/assets/4506837/20350023/d2146c4e-ac2e-11e6-89bc-983233628d09.png)

test/specs/requests.spec.js
expect(response.status).toEqual(200);
        expect(response.statusText).toEqual('OK');
        expect(response.headers['content-type']).toEqual('application/json');
        done();
      }, 100);
    });
  });
  
  it('should fix IE no content error', function (done) {
    var response;
    axios('/foo').then(function (res) {
      response = res
    });
    getAjaxRequest().then(function (request) {
      request.respondWith({
        status: 1223,
        statusText: 'Unknown'
      });
      setTimeout(function () {
        expect(response.status).toEqual(204);
        expect(response.statusText).toEqual('No Content');
        done();
      }, 100);
    });
  });
  it('should allow overriding Content-Type header case-insensitive', function (done) {
    var response;
    var contentType = 'application/vnd.myapp.type+json';
    axios.post('/foo', { prop: 'value' }, {
      headers: {