People are getting tripped up on these being unavailable in the polyfill.

Ref. #666 [ci skip]

* Mention module exports
* Expand on abortable functionality
* Remove Bower instructions since the project is defunct
* Remove Yarn instructions because they are a no-brainer

Closes #569

The Open Code of Conduct has been defunct for a while.

https://github.com/whatwg/fetch/pull/585

Improve various aspects of the language in the README, some being typos.

https://developer.apple.com/library/prerelease/content/releasenotes/General/WhatsNewInSafari/Articles/Safari_10_1.html

Hopefully this will help reduce the number of invalid issues opened.

No longer recommend es6-promise due to its size and the fact it doesn't
conform to Promises/A+. Fixes #415

Fixes #393

The adjective similar is modifying behave instead of a noun or pronoun. Use an adverb to modify a verb, adjective, or other adverb.

Microsft -> Microsoft

Fixes #401

HTTP methods are case-sensitive. The examples in the README currently
lead developers to think that this API normalizes all of the method
names to uppercase, leading to issues like #37 and #254.

Setting the right precedent in the README will prevent developers
from making mistake of trying to use method: 'patch' (or any
other verb that isn't normalized for backwards compatibility).

Closes #205.