IE 11 is giving me a hard time...

I'm trying to send some binary data as a `Uint8Array` in a POST request, but `[Object object]` gets sent instead. In IE's dev tools, inspecting the request body reveals that the `Uint8Array` is being transformed incorrectly as `[Object object]`:

![screen shot 2016-03-15 at 9 31 20 am](https://cloud.githubusercontent.com/assets/440299/13793569/b991e3ea-eab4-11e5-9901-f9adee6f1beb.png)

I tried commenting out some code to see if the request will send the correct data, and it does. I commented out these lines:

```
if (utils.isArrayBuffer(requestData)) {
  requestData = new DataView(requestData);
}
```

https://github.com/mzabriskie/axios/blob/master/lib/adapters/xhr.js#L162

... and the resulting request sent binary data as expected:

<img width="463" alt="screen shot 2016-03-15 at 7 14 07 pm" src="https://cloud.githubusercontent.com/assets/440299/13800038/27c28680-eae2-11e5-9718-512fcc078cd7.png">

What is the purpose of the `new DataView()` call? What is happening that turns the binary data into the `[Object object]` string? Why does this break only in IE 11 (works in Chrome, Firefox, Edge)?

test/specs/requests.spec.js
});
  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: {
        'content-type': contentType
      }
    }).then(function (res) {
      response = res;
    });
    getAjaxRequest().then(function (request) {
      expect(request.requestHeaders['Content-Type']).toEqual(contentType);
      done();
    });
  });
  it('should support binary data as array buffer', function (done) {
    
    if (isOldIE && typeof Int8Array === 'undefined') {
      done();
      return;
    }
    var input = new Int8Array(2);
    input[0] = 1;
    input[1] = 2;
    axios.post('/foo', input.buffer);
    getAjaxRequest().then(function (request) {
      var output = new Int8Array(request.params.buffer);
      expect(output.length).toEqual(2);
      expect(output[0]).toEqual(1);