* Rename `versions.Installed` function to `IsInstalled`
* Create `versions.Installed` function
* Create `shims.GenerateForPluginVersions` and `shims.GenerateAll` functions
* Address linter warnings
* Create asdf reshim command
* Run asdf hook from new `shims` functions
* Get asdf info BATS tests working
* Create `versions.Installed` function
* Update `versions.Latest` to return single version
* Implement `latest` asdf command
* Implement info command
* Remove duplicate and unneeded BATS tests from `main_test.go`
* remove download dir for plugin when removing plugin
* update plugins.Add function so downloads directory is created
* Create `pluginindex.Build` function
* Use `pluginindex` when no plugin URL provided for plugin add command
* Get more `plugin_add_command` BATS tests passing against Golang version
* Only use `pluginindex` when it is not disabled
* Update error message so it matches legacy format
* Add staticcheck.conf