This allows rails code to be more confdent when asking for a model name, instead of having to ask for the class.

Rails core discussion here: https://groups.google.com/forum/#!topic/rubyonrails-core/ThSaXw9y1F8

* Fix incorrectly named tests
* Restore Object#to_param behavior
* Ensure param is derived from a squished and truncated string

Reuse the already existing logic used for grabbing this information from
the updated columns.

Extend ActiveRecord::Base#cache_key to take an optional list of timestamp attributes of which the highest will be used.

- Extract max timestamp retrieval for cache_key
- Update changelog for cache_key changes

This reverts commit 637a7d9d, reversing
changes made to 5937bd02.

This can be done using the class attribute cache_timestamp_format

Conflicts:
	railties/guides/source/configuring.textile