Initial push of the spike. Nested Y.Apps works (including on browsers that don't support pushState - though still need to confirm my solution to this is officially supported by YUI).

Still to do:
- test fluid URLs before the sub-app routes e.g. having an "in context" user's name as the first part of the url /James/hi/welcome -> Hi James, welcome!
- more detailed README
- some thorough code comments