Yarı melek, yarı canavar

Thanks to @michi-zuri and all other people using #37 for over ~8 months and their patience on me having time to merge it.

Süzüleceğim yanına kadar

https://www.youtube.com/watch?v=WFg5ATD98_8

Release notes:

• the use asdf command now takes no arguments.

  Previously this command could take optional tools and versions but we removed that in favour of using asdf own version resolution.
  That means versions are specified in only one place: The .tool-version files.

• Removed old shim and now asdf-direnv uses asdf custom commands.

  For example, now you can run asdf direnv allow from anywhere.

Upgrading notes:

• If you are upgrading from a previous version, be sure to use latest asdf

• Also note that the initialization hook changed, and now the content of your ~/.config/direnv/direnvrc file should be:

source "$(asdf direnv hook asdf)"