Remove obsolete pagination docs

[gmile]

Pagination was extracted from mongoid, so remove references to #paginate method from docs.

[TomK32]

I'd prefer it if this bit is moved to the extension page instead of dropping it.

[gmile]

I got your point. I will be updating pull request soon, moving pagination docs to an extension page

[siong1987]

This has been there for more than a month. I guess this has created a lot of confusion.

Why don't we just accept this pull request first? Then, only work on that "extension".

I am actually working on this. What do you mean by extension page?

[durran]

Pagination references have been removed. Thanks!