Updated dependencies:
* Dependencies is a better/more common description than
  'required packages'.
* Ruby hasn't actually been a dependency in a very long
  tim. In fact, not since vim-pastie was removed:
  ff48b5e457e86232995833faf1ba220c5e3a9564
* Added link to exuberant ctags. Expect people who need
  this to be able to install it themself.