v1.9.1

What's Changed

• setup.py: update download url and remove python 2.6 support by @thiell in #508
• clush: select proper last parsed config file (#511) by @thiell in #512
• setup.py: improvements for pip install and venv by @thiell in #510
• correct typo 'sterr' by @haiwu in #513
• Fix typos found with codespell by @xdelaruelle in #514
• RangeSet: support negative ranges (#515) by @thiell in #518
• RangeSet: remove duplicate intiter() definition by @thiell in #519
• NodeSet: a few minor code fixes by @thiell in #520
• Release 1.9.1 by @thiell in #521

Full Changelog: v1.9...v1.9.1