Retry logic for Knack data load errors

[jillh510]

Have a way to retry data upload to Knack in case of errors

[tkell]

We probably want to log and not retry 4xx errors, and retry 5xx errors with some backoff?

Or do a very simple thing where we try everything twice, and then give up – much less good, but much easier to make.

[jillh510]

ActBlue will retry if they don't get a 2xx back from us, so I'm good with logging the failure and then returning an error code to ActBlue.

[tkell]

Closed (for now) with #23 !