Remove all references to `global-rainbow-parens-mode`

`ome-htmlize-setup` definitely has to go because it was a fix relating to the incompatibility of `global-rainbow-parens-mode` and `htmlize-mode`, since `global-rainbow-parens-mode` is removed, `ome-htmlize-setup` is no longer needed. As for `ome-rainbow-delimiters-setup`, I removed the `global-` prefix, which means that users have to turn on `rainbow-delimiters-mode` on a case by case basis, instead of globally.

The resulting version of `oh-my-emacs` works well on Ubuntu 14.04 LTS.