updated version and made the header its only source of truth (#144)

* updated version and made it only source of truth

* bumped Version number

[ROCm/rocshmem commit: ca5fdd4718]

projects/rocshmem/include/rocshmem/rocshmem.hpp

@@ -52,7 +52,7 @@
 
 namespace rocshmem {
 
-constexpr char VERSION[] = "2.0.0";
+constexpr char VERSION[] = "3.0.0";
 
 /******************************************************************************
  **************************** HOST INTERFACE **********************************