I prefer to have it as ftplugin/erlang_refactor.vim

As /VIMPATH/ftplugin.vim says, it should load with no trouble:

  exe 'runtime! ftplugin/' . name . '.vim ftplugin/' . name . '_*.vim ftplugin/' . name . '/*.vim'
                                                                ^^^

Conflicts:
	ftplugin/erlang_refactor.vim
Rename option to a more standard name: g:erlangWranglerPath