Update hash_set_m.h

Author: hordi

include/hash_set_m.h

@@ -5,7 +5,7 @@
 // Fast hashtable (hash_set, hash_map) based on open addressing hashing for C++11 and up
 //
 // This version supports full size_t hashing (calculates hash of each elements after any reallocation/resize) 
-// version 1.3.0
+// version 1.3.1
 //
 // https://github.com/hordi/hash
 //