ENH: API for batch call

Would be nice for a helper function that takes the updater class (all nicely set up) to apply `run` method on a list of repos. This list should be chunked. Within each chunk, maybe `time.sleep(0.5)` between calls. Between chunk, maybe `time.sleep(10)` or something, to hopefully not trigger GitHub spam killer. This function will return a list of repos that fail for whatever reason, for manual follow-up (like a second run).