made mytree() an unbiased tree -> still lots of overfitting though...
further touch-ups in examples and text



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/partykit@519 255f4249-2263-4417-b1ea-8498779e27a7
small fixes

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/partykit@520 255f4249-2263-4417-b1ea-8498779e27a7