This implements the ActiveModel::Serializer object. Includes code, tests, generators and guides.
From José and Yehuda with love.
Conflicts:
railties/CHANGELOG.md
Reasons:
* Markdown reads well as plain text, but can also be formatted.
* It will make it easier for people to read on the web as Github
formats the Markdown nicely.
* It will encourage a level of consistency when people are writing
CHANGELOG entries.
The script used to perform the conversion is at
https://gist.github.com/1339263