Identify & remove content that is blatantly duplicative of API docs

[ajpiano]

As we discussed once upon a time in #39, we shouldn't have pages that are simply API reference, that's what the API docs are for.

[ajpiano]

https://github.com/jquery/learn.jquery.com/blob/master/page/ajax/jquery-ajax-methods.md - fixing this is part of #64

[arthurvr]

Opened #591 too.