On: Gradual type checking for Ruby

[damncabbage]

In case the question is actually "Why not 1.9.3?", it's likely because 1.9.3 is End Of Life, and doesn't even get security upgrades now:

https://www.ruby-lang.org/en/news/2014/01/10/ruby-1-9-3-will...

https://www.ruby-lang.org/en/news/2015/02/23/support-for-rub...