fix(docs): Migrate to rouge [ci skip]

[KapilSachdev]

Closes #1336

[mcmire]

Oops, looks like the PR I just merged created conflicts, would you mind rebasing this?

[mcmire]

Okay, this looks good. I just tried running bundle exec yard doc and something must be screwy with the version because for some reason I'm getting docs for all of the private classes/methods instead of them being excluded. But I don't think these changes have anything to do with that, that's a separate issue.

[KapilSachdev]

@mcmire as all documentation related issues are fixed now, can you please release the missing documentation of all the versions released after 4.3.0.

[mcmire]

@KapilSachdev Yup! Regenerated docs for v4.4.0 and v4.4.1. If you went to http://matchers.shoulda.io/docs/ recently the redirect may be cached, but it should shortly redirect you to v4.4.1.

[vsppedro]

What do we need to do to update the list of matchers on this page? - https://matchers.shoulda.io/

If I'm not wrong, the accept_nested_attributes_for is deprecated and because of that is not even on the README anymore.

Besides that it's missing some matchers like: have_rich_text, have_one_attached, have_many_attached, have_implicit_order_column and maybe others.

[mcmire]

@vsppedro Good point! I totally forgot about that page.

The code for that page is kept in the gh-pages branch along with the documentation. I have a notice in that branch that says you shouldn't update that branch directly but in this case it would be fine. The home page is kept in index.html (sorry, I'd forgotten it's just one big HTML file — there might be a more maintainable way we can organize that code).