Don't prefix the name with attribute_. Avoids a string allocation on
read_attribute, which is a bit faster.

This means we never have to rely on define_method (which is slower and
uses more memory), even when we have attributes containing characters
that are not allowed in standard method names.

(I am mainly changing this because the duplication annoys me, though.)

Also make it actually work.

It slows down all read_attribute accesses to map 'id' to whatever the PK
actually is, inside read_attribute. So instead make sure the necessary
methods are defined and that they redirect wherever they need to go.

This is good because it reduces duplication.

This makes me happy!

Define singleton methods on the attributes module instead. This reduces
method pollution on the actual model classes. It also seems to make
something faster, I am unsure why! O_o

* A Railtie API for registering new exceptions and their respective status code (check Active Record railtie for an example)

* Extraction of ShowExceptions middleware logging and debugging features into a middleware called DebugExceptions

Conflicts:
	actionpack/CHANGELOG.md

Revert "Added ActiveRecord::Base#last_modified to work with the new fresh_when/stale? conditional get methods from Action Pack"

Needless indirection with no added value.

This reverts commit 535853e8.

Added ActiveRecord::Base#last_modified to work with the new fresh_when/stale? conditional get methods from Action Pack

default_asset_host_protocol should not default to :relative

When default_asset_host_protocol is left as nil, it will use absolute protocols when a request is present, and relative protocols otherwise (eg in asset generation)

Fix argument error message for length validation

Add hackery to make Syck use encode_with/init_with. Fixes 1.8 after recent changes to attribute serialization.

Implement a mini state machine for serialized attributes. This means we
do not have to deserialize the values upon initialization, which means
that if we never actually access the attribute, we never have to
deserialize it.