Add vim html5 plugin
Vim config

- Change NERDTreeFind shortcut from `<leader>r` to `<leader>f`.  I never
  remembered the former.

- Don't move the cursor backward when returning to Normal Mode from
  Insert Mode.
Python environment

- alias `py` to `python`
- add `~/.pythonrc` file
- python shell autocomplete
- python shell remember history across sessions
Upgrade oh-my-zsh
Vim: fix config for snippets