Validate exit codes more thoroughly. C'mon, Cory.

src/main.c

@@ -516,7 +516,7 @@ static int _tf_command_run(const char* file, int argc, char* argv[])
 
 	if (args.count == 1)
 	{
-		_tf_run_task(&args, 0);
+		result = _tf_run_task(&args, 0);
 	}
 	if (args.count > 1)
 	{