Backoff and retry if API rate limit exceeded

[gaddman]

If the API rate limit is exceeded an error is generated and the metric is lost. Support for a backoff and retry mechanism would prevent the loss of data in the event the limit is exceeded and is a requirement for us to use this package. Since the API error code doesn't provide any information about the limit, a simple retry such as wait a few seconds and repeat a few times would be an improvement.