emacs: add ensime for scala
zsh: zkbd bindings (if needed)
zsh: remove zkbd
zsh update: use [oh-my-zsh](http://github.com/ahilsend/oh-my-zsh)

* Move custom prompt to oh-my-zsh as a theme ahilsend/oh-my-zsh@6f1eb9161ef547c8790adc4f04719b506e1580c0
* Add some aliases
* add per-directory-history