Add script to install everything with stow.
ZSH: initial commit of `.zshrc`.
Silence pushd/popd in install script.
ZSH: Setup ZSH completion, set default editor.

With current setup, `vi` still points to `vi`, not `vim`. So we
must explictly set the alias and the name of the default editor.
VIM: Introduce initial vim setup.
ZSH: Fine-tuning, setup prompt.
GIT: Add global gitignore file.
TMUX: Add tmux config (use a terminal with colors).
TMUX: Rebind prefix to ctrl+s.
TMUX: Enable vi mode.
ZSH: Use Emacs-style keybindings for now.
TMUX: Setup custom keyboard shortcuts.
VIM: Install plugins, fix backspace key, autoremove trailing spaces.
ZSH: Improve detection of dirty state of git repos.
VIM: Setup ruler and automatic text wrapping.
Add README file.