Revert "Use hybrid line numbers"

This reverts commit 397b415f476d39c99f1a7189579e8406faa34e33.
Add diff-highlight script and configure with git
Remove <Leader>sd Vim mapping

Alternative mappings are <Leader>sw or <Leader>r.
Switch to @hackling's vim-surround config

It doesn't add spaces when surrounding with parens, brackets, or parens.
Tweak styles for the jellybeans_nate Vim colorscheme
Add @twe4ked's vim-diff-toggle Vim plugin
Replace quickfixsigns_vim with vim-gitgutter
Add vim-ruby-refactoring Vim plugin