remove rvm and add rbenv
Merge branch 'master' of https://github.com/Dextro/dotfiles

* 'master' of https://github.com/Dextro/dotfiles:
  add powerline theme to oh-my-zsh themes
  add oh-my-zsh powerline theme
  add oh-my-zsh
  remove submodules
  add oh-my-zsh and oh-my-zsh-powerline-theme
  remove submodules oh-my-zsh
update oh-my-zsh