[fetch] Tests (#62)

We need tests for `fetch()` (and Fetch in general) in https://github.com/w3c/web-platform-tests as currently http://w3c-test.org/fetch is rather lacking. For `fetch()` a bunch from XMLHttpRequest can probably be reused, though it probably requires going through all the tests one-by-one.

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/62