POST to /pins can time out

[corajr]

Often once or twice a day, attempts to POST to the /pins endpoint end in a server timeout (see H13 error). I'm not sure of all the ways this might occur, but I suspect uploading large images can contribute to this issue (as we don't respond until the entire form is submitted).

Image uploads should be able to run separately from the form submission or at least not cause the request to timeout. Direct uploading to S3 (via Javascript) is one possible solution.