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.

fix exception page when template contains utf-8 and parameters contain utf-8

update guides for the namespace option in form helpers