zipfR 0.6-8: zipfR tutorial converted into genuine vignette

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/zipfr@26 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated tutorial PDF on Web page

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/zipfr@27 edb9625f-4e0d-4859-8d74-9fd3b1da38cb