Added `verisions` option for `homebrew` completion

plugins/brew/_brew

@@ -35,6 +35,7 @@ _1st_arguments=(
   'update:freshen up links'
   'upgrade:upgrade outdated formulae'
   'uses:show formulas which depend on a formula'
+  'versions:show all available formula versions'
 )
 
 local expl
@@ -71,7 +72,7 @@ case "$words[1]" in
         _brew_installed_formulae
         _wanted installed_formulae expl 'installed formulae' compadd -a installed_formulae
       fi ;;
-  install|home|homepage|log|info|abv|uses|cat|deps|edit|options)
+  install|home|homepage|log|info|abv|uses|cat|deps|edit|options|versions)
     _brew_all_formulae
     _wanted formulae expl 'all formulae' compadd -a formulae ;;
   remove|rm|uninstall|unlink|cleanup|link|ln)