Allow documentation of enum variant

[Yamakaky]

Example:

quick_error! {
    /// An awesome error.
    #[derive(Debug)]
    pub enum IoWrapper {
        /// A cool variant
        Io(err: io::Error) {
            from()
        }
    }
}

[tailhook]

Docs work for me. What error do you get? Does the warning missing_docs get suppressed?

[Yamakaky]

Wow, I'm sorry, in fact it works...