Support function to rename symbol on RenameClass command

e.g.
    $Foo::Bar::GLOBAL_VAR
     ~~~~~~~~ Rename here

    $Foo::Bar::Buz::GLOBAL_VAR # <= Don't rename
               ~~~ cuz here name space exists, so both are different
Merge pull request #25 from hitode909/support_rename_symbol_on_rename_class_command

Support function to rename symbols on RenameClass command