modified publications.Rmd

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mboost@785 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
update

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mboost@786 edb9625f-4e0d-4859-8d74-9fd3b1da38cb