display 304s

Since the cached responses (304s) carry an old date, we cannot expect every response to have a newer date than the previous.

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https://trello.com/c/x1n7WtOK/67-sporadic-autocomplete-drop-down

Issue:

http://pelias.mapzen.com

Do some searches, backspace over previously entered characters, re-enter them. I frequently do not get a dropdown rendered, despite the server response being either a 200 or a 304.