Support for more containers

It's really useful that http_serde now supports Option (#4 (closed)), but I'm hitting on the issue that it doesn't support Vec. I've tried to put a PR together, but my understanding of Serde is letting me down. Would it be possible for this crate to support Vec of each of the http types, e.g.:

#[serde(with = "http_serde::vec::authority")]
authority: Vec<Authority>,

In principle, it might also be useful to support Result and HashMap too, but I don't have an actual use-case for those yet so they're not as important to me.