Added stream as class level method to make it explicit when to stream.
Render also accepts :stream as option.

Fix test_load_save in test/cases/binary_test.rb (thanks @tenderlove for actually working out how to fix it)

Bring back some bits of documentation for scopes which were removed as part of the reversion in 256b363e

Revert "Deprecate defining scopes with a callable (lambda, proc, etc) via the scope class method. Just define a class method yourself instead."

This reverts commit f0e198bf.

Conflicts:

	activerecord/test/models/post.rb

activesupport/test/json/encoding_test.rb need Json to pass against with Jruby

* 'identity_map' of https://github.com/jasoncodes/rails:
  Bypass IdentityMap in PostgreSQL geometric tests.

The identity map cache prevents us from seeing the DB formatted strings.

Add more tests, ensure we never yield outside the fiber context and that we swap buffers when moving from parent to child.

Yo dawg, I heard you like streaming. So I put a fiber, inside a block, inside a body, so you can stream.