0) brew install vim
1) brew install ack
2) brew install ctags

3) install vundle
  see here:
  https://github.com/gmarik/vundle

4) generate ctags for the rbenv ruby standard library
see here:
  https://github.com/tpope/rbenv-ctags
5) install gem-ctags
  https://github.com/tpope/gem-ctags
6) brew install the_silver_searcher