Implement "hub" subcommands simple completion

ref.
  http://blog.glidenote.com/blog/2012/05/03/zsh-completion/
  http://gihyo.jp/dev/serial/01/zsh-book/0005
  http://gihyo.jp/dev/serial/01/zsh-book
Implement copying a page title to clipboard

ref.
  http://www.mozdev.org/pipermail/vimperator/2008-October/002547.html
  https://code.google.com/p/vimperator-labs/