Initial zsh configuration

- Use antigen for package and theme management
- Set up some reasonable configuration settings to be expanded upon
  later
More updates to Vim and zsh files

- Move antigen usage before other zsh config lines to override unwanted
  settings from oh-my-zsh library
- Add some more useful plugins from oh-my-zsh
- Change some file listing aliases (lal to ll with some new flags)
- Add leader shortcuts for common fugitive commands