Update tmux, urxvt, xmodmap, vim and setup scripts

  1. Add .tmux.conf file to setup C-j as the secondary prefix
     key, eliminate the delay associated with Escape key and set
     the TERM environment variable such that Vim is able to use
     256 colours.
  2. Write a simpler .Xresources file for rxvt-unicode that uses
     a larger font to display text in the terminal.
  3. Write two separate scripts, caps and nocaps, to map or
     unmap Caps Lock to Escape.
  4. Add new commands to .vimrc file to show partial commands in
     Vim, hide buffers on abandoning them, recognize *.md files
     as Markdown files and use a larger GUI font size.
  5. Add delete feature in the setup script.