corrected path to rendr information

tools/rendr/rendr_utils.sh

 
 ## test if present in PATH
 if [ -z "$(which rend.R  2>/dev/null)" ]; then
-    echo "rendr.R is not installed. See https://github.com/holgerbrandl/datautils/tree/master/R/rendr for details" >&2
+    echo "rendr.R is not installed. See https://git.mpi-cbg.de/bioinfo/datautils/tree/master/tools/rendr for details" >&2
     exit 1
 fi