wilson method for proportions

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/correg@435 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
working version

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/correg@436 edb9625f-4e0d-4859-8d74-9fd3b1da38cb