oktest 1.5.0

Oktest.rb is a new-style testing library for Ruby. You can write `ok {1+1} == 2` instead of `assert_equal 2, 1+1` or `expect(1+1).to eq 2`. In addition, Oktest.rb supports **Fixture injection** feature inspired by dependency injection and **JSON Matcher** feature similar to JSON schema. See https://github.com/kwatch/oktest/tree/ruby/ruby for details.