add custom completion support

oh-my-zsh.sh

 # Initializes Oh My Zsh
 
 # add a function path
-fpath=($ZSH/functions $fpath)
+fpath=($ZSH/functions $ZSH/completions $fpath)
 
 # Load all of the config files in ~/oh-my-zsh that end in .zsh
 # TIP: Add files you don't want in git to .gitignore