Bump hacking to 0.9.x series

Require at least 0.9.1 because 0.9.0. had a minor bug.

This change also fixes all found issues.

Rewrote some docstrings to fit H405.

Change-Id: Ifeef11b783dbe70b2652d2b9ea29d5b20f69f2ce
Merge "Bump hacking to 0.9.x series"