Release of Version 2.4.0

Changed

• Support rake version 11.0 or higher＆rspec version 3.4.0 or higher
• Fix title of README
• Change a test with github actions
• Made it possible to run tests on ubuntu-18.04 and ubuntu-20.04
• Fix the homepage entry in predictor.gemspec

BREAKING CHANGES

• Ruby 2.1 ~ 2.5 will no longer be supported because of eol

2.3.1

Bump version

2.0.0.rc1

Major upgrade from v1.0.0 with a few breaking changes. Experimenting with a release candidate for v2.0.0

Initial release

v1.0.0

Update version