Changes:
* PyNMRSTAR automatically retries fetching an entry from the BMR API using an exponential backoff if rate limited.
* PyNMRSTAR now lists the package `requests` as a requirement, which allows it to significantly speed up fetching entries
from the database. It will still work if requests is not installed though, as in the case where you have checked out
the code locally and don't have requests installed - you just won't get the enhanced performance.
Breaking changes:
* The default value of skip_empty_loops of the method write_to_file() for both Entry and Saveframe has
been changed to True to write out empty loops. Technically according to the NMR-STAR format, empty loops should
be omitted. In practice, many libraries fail to treat a missing tag as equivalent to a present but null tag, and
would be confused by the fact that reading in a file and writing it back out again would cause these empty loops to
go missing. You can still manually specify skip_empty_loops=True to maintain the previous behavior.