Jasig/uPortal — pull request #272 by apetro (2014-03-17 14:29:12+00:00)
Title: add README.md to fragment-layout directory.

Document, right next to where one makes these edits,
* usage of `username` attribute rather than implying username from file name.
* Node ID uniqueness constraint beyond that expected of `ID` attribute in XML.
* Thoughtfulness advisable in re-using and avoiding re-use of node `ID`s.