http.async.client.status.proxy doesn't implement iterate, needed for newer cheshire versions

[jwhitlark]

The error is (roughly):

java.lang.UnsupportedOperationException:  iterator

on 

http.async.client.status.proxy$clojure.lang.APersistentMap

We've worked around it, but I wanted to document it, and it doesn't seem that hard to fix, if someone was so inclined.