Signed-off-by: NJosé Valim <jose.valim@gmail.com>

We can't assign @view_context_class here, define super() in test instead if we want to avoid warnings.

'The scheme name consists of a letter followed by any combination of letters, digits, and the plus ("+"), period ("."), or hyphen ("-") characters; and is terminated by a colon (":").'

Removed non-functional links.
Removed links to API documentation.
Removed link to Rails 2 material.

Renamed "References" to "Further Reading".

These plugins are obsolete even for Rails 2, they have no place in a Rails 3 guide.
Also removed "mad cool" reference.

If anyone has ideas about cache plugins that *must* be included, I would love to know.
As far as I am concerned the rails guides should stick to built-in methods and have a
simple list of references for people wishing to investigate further.

I will check out the references after this commit to see if they're up to date.

Avoid (@_var ||= nil) pattern by using initialize methods and ensuring everyone calls super as expected.

[#5723 state:committed]

performance improvement based on discussion at http://github.com/rails/rails/commit/fbd1d306b95cc2efb6422e12d26d5818a3a42343

Credit goes to all the participants in the discussion

This reverts commit bee447a5.