https://fetch.spec.whatwg.org/#atomic-http-redirect-handling

See #30 for details.

Previously renamed to _body to detect these types of errors.

The body must be consumed through the `text`, `json`, `formData`, or
`blob` functions.

IE 9 fails on 204s with error code 1223
http://www.enhanceie.com/ie/bugs.asp

Rewrite the code back to 204. Note: response headers remain unavailable
in this case. This was fixed in IE 10.

Reject all HTTP codes that are not in the 100..599 range.

When an empty reply is received from the server, `xhr.onerror` callback
should get triggered. IE 9, however, triggers the `onload` callback with
status code 12152 that stands for:

    ERROR_HTTP_INVALID_SERVER_RESPONSE
    The server response could not be parsed.

http://support.microsoft.com/kb/193625

IE caches xhr responses pretty aggressively and after restoring the
previous response from cache, it blanks out the "Date" header (probably
by design). The solution for this test is to use a cache-busting query
parameter.

PhantomJS doesn't seem to send request body for PATCH:
https://github.com/ariya/phantomjs/issues/11384

Now only the whitelisted method names get normalized by uppercasing and
the rest are left untouched since HTTP method names in general are
case-sensitive.

In tests we must use `PATCH` (uppercase) because Node.js server doesn't
support `patch` (lowercase).

This fixes PUT/DELETE for IE 9 and PATCH for Node.js.

Ammended tets to also check error message, not just type.