vignette added in inst/doc

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sintro@249 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
vignette added in inst/doc

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/sintro@250 edb9625f-4e0d-4859-8d74-9fd3b1da38cb