IE 9+ fixes

* Fix making PUT/DELETE requests by uppercasing the HTTP method name
* This also fixes PATCH for Chrome/Safari
* Fix requests with undefined body on IE
* IE 9 fix for connection error
* Fix CSS being applied to test suite

The only test that now fails is the FormData test on IE 9. Maybe we should skip that test if FormData is unavailable?
Actually [the spec explicitly states](https://fetch.spec.whatwg.org/#dom-request) that `Request` constructor should normalize the method by uppercasing it:

```
14. If init's method member is present, let method be it and run these substeps:

  1. If method is not a method or method is a forbidden method, throw a TypeError.
  2. Normalize method.
  3. Set request's method to method.
```