updated google group

Author: JensWehner

README.md

@@ -25,7 +25,7 @@ use this package, please cite the VOTCA papers:
   J. Chem. Theo. Comp. 5 (12), 3211 (2009) 
 
 In case of questions, please post them in the google discussion group
-for votca at http://groups.google.com/group/votca-xtp
+for votca at [here](https://groups.google.com/forum/#!forum/votca)
 
 You can contact the VOTCA Development Team at devs@votca.org.