Merge branch 'issue/integrate_parallel' into 'master'

sum up parallel integrals

See merge request !70

src/amdis/Integrate.hpp

@@ -28,7 +28,7 @@ namespace AMDiS
         localFct.unbind();
       }
 
-      return result;
+      return gridView.comm().sum(result);
     }
 
     template <class GF, class GV, class QP>