Improve up/down-line binding.
Improve up/down-line binding.

Use up-line-or-beginning-search/down-line-or-beginning-search by default
and bind up-line-or-search/down-line-or-search to C-up/C-down.

blueyed/oh-my-zsh,blueyed/oh-my-zsh,blueyed/oh-my-zsh