2.1.1

The release simplifies the code by removing elements that are no longer necessary, addresses a few issues and improves the automatic build and test GHA workflows.

Pandas 1.3+ causes issues with trading-calendars; while we work out migration to the more actively maintained exchange_calendars, pandas is temporarily limited to version <=1.2.5.

Big shout-out to @MBounouar who made quite a few very useful contributions, namely:

• Migrate from nosetest to pytest (#9, #15 )
• Apply patch for futures backtesting (#3)
• Various revisions of the Cython extensions to facilitate maintenance and enhancements going forward (#46, #49)
• Address warnings and other maintenance issues.

In addition, there are several improvements to the automatic test and build process (#47, #48, #50, #51, #52).