Integration with VimColor

The Wiki plugin doesn't work very well with the VimColor plugin. Wiki interprets the code as wikitext, which breaks the syntax highlighting.

This can be fixed by protecting everything between VimColor's start and end tags. Since this can be dangerous if VimColor isn't running, it should have an option to disable it.

I have attached a patch that should do the trick. It works fine on my local system, assuming that VimColor runs after Wiki.