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Features
* Added a mechanism which makes sure the library doesn't send requests too fast to BGG, triggering their protection
(HTTP error 503). It does this by serializing all the requests and making sure there's enough waiting time between
them so that the configured `requests_per_minute` is respected.
Fixes
* Fixed the retry mechanism, allowing retries=0 (meaning no retries at all). Before, the code would fail if the user
specified retires=0