Changed agnoster theme from a submodule to a local file.

Also added parse_git_dirty and get_short_dir into the theme file
Changed $EDITOR and $VISUAL to vim
Prefer old prompt style
Prompt theme copied from
https://github.com/paradox460/prezto/blob/paradox/modules/prompt/functions/prompt_paradox_setup
Enabled module git and syntax-highlighting
Transfered the customization from bash to zsh