zshrc: add a "ruby" machine type

Did some ruby stuff to play with jekyll. Add a machine type for it so it
gets loaded when appropriate.
zshrc: remove a bunch of oh-my-zsh comments

Don't need this clutter any more. Just left a few things that I might
want. Also removed the perl and history-substring-search plugins
zshrc: add a bunch of custom vim bindings

Customize vi-mode like wow. Should move this into a custom vi-mode plugin.