update: add verbose option in help message

include/constant.h

@@ -50,8 +50,11 @@ ClearDNS usage:\n\
   Options:\n\
     --debug    Enable debug mode.\n\
     --config   Specify config file. (default: cleardns.yml)\n\
+    --verbose  Output verbose log content.\n\
     --version  Show version information.\n\
     --help     Print this message.\n\
 "
 
+// TODO: add verbose option
+
 #endif