Fix #2572 and define fixture table name in the associated model

AS::Callbacks: remove __define_runner

refactor Range#include? to handle ranges with floats

Renamed "fixture_name" to "accessor_name" and made fixture names in the form "admin/users" be used as the key for the hashes @fixture_cache and @loaded_fixtures.

Previously the variable "fixture_name" here was getting a value of the form "admin_user", and this value was then used as the hash key.

Made the fixture's table name be taken from its model class whenever this class responds to table_name, instead of inferring it sometimes from the fixture's pass.

The previous behavior seemed buggy because it depended on whether the model class was passed as a constant or as a name string.

Improved Fixtures#initialize.

This solves an issue with set_fixture_class class method caused by create_fixtures method's overwriting passed to it fixture model classes, when the fixtures are "namespased": foo/bar or admin/users.

The idea is to use "foo/bar" string as the name and identifier of a
fixture file bar in directory foo.  The model class of the fixture is either set with set_fixture_class method, or otherwise inferred from its name using camelize method.

Also a bug is fixed in lines 487-489 when the table names were guessed by substitution from the fixture file names, ambiguously called  table_names, instead of being taken from fixture attributes.  Now they are taken from attributes.

I plan to submit another fix so that the fixture's table name (for
example foo_bar) be defined by the fixture's model whenever possible,
instead of inferring it from the fixture's name ("foo/bar").

Test using fixtures with random names and model names, that is not following naming conventions but using set_fixture_class instead.

It is expected that the table name be defined in the model, but this is not explicitly tested here.  This will need to be fixed.

rather than casting

content_for with flush parameter

worry about "inspect" marshalling

ivars in clear!

remove ruby 1.8 checking in constantize method

Fix rails/generators/base.rb documentation for hook_for

is one benefit of choosing composition over inheritance.

allow reorder to affect eager loading correctly