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
response = res;
    });
    getAjaxRequest().then(function (request) {
      request.respondWith({
        status: 200,
        statusText: 'OK',
        responseText: '{"foo": "bar"}',
        headers: {
          'Content-Type': 'application/json'
        }
      });
      setTimeout(function () {
        expect(response.data.foo).toEqual('bar');
        expect(response.status).toEqual(200);
        expect(response.statusText).toEqual('OK');
        expect(response.headers['content-type']).toEqual('application/json');
        done();
      });
    });
  });
  it('should supply correct response', function (done) {
    var response;
    axios.post('/foo').then(function (res) {
      response = res;
    });
    getAjaxRequest().then(function (request) {
      request.respondWith({
        status: 200,
        statusText: 'OK',
        responseText: '{"foo": "bar"}',