* Add ruby 2.6 test
* Fix broken tests
* Fix compatibility test
* Fix bundler version
* Use new docker image
* Fix broken test
* Use new docker image in ruby26 test
* Install ruby for mac
* Add continuous test for ruby 2.3, 2.4 and 2.5
* Change ruby 2.5 to 2.5.0
* No need to provide argument to rb_funcall when argc is 0
* Fix tests for ruby 2.5
* Use rescue instead of assert_raise to accept subclass of error