Wren 0.1.0!

There's nothing new in this "release", but now is as good a time as any
to start versioning. Going forward, I plan to do periodic releases and
update the changelog so users can see what's going on.

src/cli/vm.c

@@ -257,7 +257,7 @@ int runRepl()
   initVM();
 
   printf("\\\\/\"-\n");
-  printf(" \\_/   wren v0.0.0\n");
+  printf(" \\_/   wren v%s\n", WREN_VERSION_STRING);
 
   char line[MAX_LINE_LENGTH];