0.9.12

KInd of hoping this is the last 0.9 release, and I find time to stablize as 1.0, and start the 2.0 work some time soon...

Changelog:

• Remove Cyclic references (memory leak)
• Add left & right shift operations (<< and >>)
• Switch to GH actions & CodeCov.io for CI tests
• Add extra contributors details
• Reformat w/ Black + isort, and have linting of those in CI