Updates to HTTP error handling. Previously, there was a general mechanism to retry 3 times for every error. This retry mechanism had a backoff design, but there was not a long enough delay duration to recover from a rate limit error with the premium tier of Twitter search. It also treated all errors the same, retrying three times even if your credentials were wrong.

So, this new update does the following:

• With rate limit errors, it backs off exponentially across a fifteen-minute period and should recover from such errors and continue on.

• Retries with 5xx server-side errors, 30 seconds between retries.

• All other errors (4xx) are treated as "one and done, no use in retrying..." errors.