* Improve Rakefile
* Remove intermediate files
* Remove unnecessary manipulations from extconf.rb
* Add README and LINCENSE to source files
* Manage ext source files using YAML file
* Use extsources.yaml to include files into gem package file
* Add git-managed source files to build dependency
* Add test task
* Download model for test if not exists
* Add test for build
* Ignore gem package directory
* Enable GitHub action for Ruby binding
* Fix model name
* Build lib file for test
* Use extension for each platform
* Use extension for each platform on testing
* Move built lib file rather than copy
* Add intermediate files to clean targets
