input elements don't get key from props

[callum-oakley]

Most elements let you provide a :key either in metadata or in the props, but providing a :key to an :input element in props doesn't appear to work. I haven't looked at the code very deeply, but something to do with the special casing for :input and :textarea? For example, on v1.0.0:

(.-key (r/as-element           [:input {:key 0}])) ;=> nil
(.-key (r/as-element ^{:key 0} [:input]))          ;=> "0"
(.-key (r/as-element           [:div   {:key 0}])) ;=> "0"
(.-key (r/as-element ^{:key 0} [:div]))            ;=> "0"

Obviously not a showstopper since I can just use metadata instead. :)