adapated to new model.design strip.terms

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/timereg@351 edab9b15-3c32-4f9a-a569-739a535b425d
added testthat

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/timereg@352 edab9b15-3c32-4f9a-a569-739a535b425d