Change Leader keystrokes (Vim)

- Use \v to verticaly split a window
- Use \so to write and source the current file
- Add \\ shortcut to quickly open `~/.vimrc`
Update README.md (Add link to LICENSE file.)
Update i3status configuration

- Remove system load from i3bar
- Display the battery status (use battery 1 instead of 0)
- Don't show the ip address of wlan and ethernet