Issue 2264: update readme

https://code.google.com/p/otwarchive/issues/detail?id=2264

This is a documentation change, but since it's a very visible documentation change, please give feedback if anything seems missing or incorrect or too much information. :) The link to the footer is also updated to point to the same license (GPL v2).
Maybe do the full name for extra clarity? And a full stop, because why not:

"by the [Organization for Transformative Works](http://transformativeworks.org)."