update version number to v0.5

Author: yangbai90

src/main.cpp

@@ -25,9 +25,9 @@ int main(int args,char *argv[]){
     ierr=PetscInitialize(&args,&argv,NULL,NULL);if (ierr) return ierr;
 
     const PetscInt Year=2021;
-    const PetscInt Month=1;
-    const PetscInt Day=1;
-    const PetscReal Version=0.4;
+    const PetscInt Month=3;
+    const PetscInt Day=28;
+    const PetscReal Version=0.5;
 
     Welcome(Year,Month,Day,Version);