Update to 1.13.0

Changelog:

• Added a new --shell=none/-N option to disable the intermediate shell for executing the benchmarked commands.
• Added --setup/-s option that can be used to run make all or similar.
• The -s short option for --style is now used for the new --setup option.
• Improved documentation and test coverage, cleaned up code base for future improvements.

Ran hyperfine --min-runs 5 'sleep 0.2' and got the benchmark result successfully.