Document content_transformer()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tm@1358 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated.


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tm@1359 edb9625f-4e0d-4859-8d74-9fd3b1da38cb