Integrate opp.zsh, "vim text-objects" for Zsh

[tannhuber]

I use opp.zsh which works great with prezto. However, in order to avoid conflicts in the future it might be a good idea to have this functionality directly in prezto. What do you think?

[Fl4t]

Need !

[sorin-ionescu]

There are a few external modules in Prezto, syntax-highlighting, for example. As long as it's loaded after the editor module and to the end of the modules list, it should be OK.

[sorin-ionescu]

A pull request has been opened in #636.