Skips benchmark test if there are no C-extensions

Updated roadmap in README

Fixed an issue described in #101, other minor improvements

Minor fix to ensure variables less than one are tracked where required

Updated README

Updated dependencies, adjusted number of wheels expected, bumped version

Added Ubuntu 22.04 to publish to attempt building wheels for older ma…

…nylinux versions

Bumped version number and updated dependencies

Adjusted the threshold for performance benchmarks

Changed development status from beta to production