Fixing compile error on platforms/filesystems that are case insensitive (MAC) due to MPI.h including mpi.h which included itself rather than including mpi

tests/BasicSimulator.cpp

@@ -5,7 +5,6 @@
 #include <exception>
 #include <stdexcept>
 #include <fstream>
-#include <mpi.h>
 
 #include "pmmc.h"
 #include "Domain.h"
@@ -13,6 +12,7 @@
 #include "D3Q19.h"
 #include "D3Q7.h"
 #include "Color.h"
+#include "common/MPI_Helpers.h"
 #include "Communication.h"
 
 //#define CBUB