Update release notes for 4.0.0b1 (pynamodb#611)

Stop using requests in favour of botocore & urllib3 (pynamodb#580)

Release notes for v3.3.3

version 3.3.2

version 3.3.1

version 3.3.0

Use attr.get_value(value) when deserialize (pynamodb#450)

change update & update_item to use attr.get_value(value) in deserilazation

Return the correct last_evaluated_key for limited queries/scans. Fixes …

…pynamodb#406 (pynamodb#410)

3.2.1 (pynamodb#390)

2.2.0 -- minor release to prepare for upgrading to 3.0.1