The README.txt file refers to the 4.3.0 Quickstart docs

The README.txt file refers to the 4.3.0 Quickstart docs. It should refer to whatever the current version we're on is.
http://oozie.apache.org/docs/4.3.0/DG_QuickStart.html

It might be a good idea to update our website with a /docs/current/*.html site so that we don't have to keep updating this, as long as we update the "current".