use feature names instead of failing branch names in "git flow feature"

plugins/git-flow/git-flow.plugin.zsh

@@ -237,13 +237,13 @@ __git-flow-feature ()
 
 				(diff)
 					_arguments \
-						':branch:__git_branch_names'\
+						':branch:__git_flow_feature_list'\
 				;;
 
 				(rebase)
 					_arguments \
 						-i'[Do an interactive rebase]' \
-						':branch:__git_branch_names'
+						':branch:__git_flow_feature_list'
 				;;
 
 				(checkout)
@@ -254,7 +254,7 @@ __git-flow-feature ()
 				(pull)
 					_arguments \
 						':remote:__git_remotes'\
-						':branch:__git_branch_names'
+						':branch:__git_flow_feature_list'
 				;;
 
 				*)
@@ -334,4 +334,4 @@ __git_command_successful () {
 	return 0
 }
 
-zstyle ':completion:*:*:git:*' user-commands flow:'description for foo'
\ No newline at end of file
+zstyle ':completion:*:*:git:*' user-commands flow:'description for foo'