document histogram setMethodData (#22)

include/ALL.hpp

@@ -498,6 +498,10 @@ public:
   /// balancing methods
   /// @param[in] data pointer to a struct or other data object in the format the
   /// methods requires
+  ///
+  /// For the histogram method the number of bins per dimensions can be given
+  /// as a C array of `int`s. The length of the array must be the number of
+  /// dimensions given to the load balancer. BE CAREFUL this is not enforced!
   void setMethodData(const void *data) {
     balancer.get()->setAdditionalData(data);
   }