fix name schema for sudo plugin

Plugin won't load automatically if added to variable $plugins, if name schema different than $name/$name.plugin.zsh is used (see is_plugin() in oh-my-zsh.sh).
Merge pull request #2368 from lumbric/master

fix name schema for sudo plugin
Merge branch 'master' of https://github.com/robbyrussell/oh-my-zsh