Update off of Ruby 2.3 (and update to Rails)

[wwahammy]

Currently, Houdini uses Ruby 2.3 and the latest version of Rails 3.2. Ruby 2.3 is in security maintenance mode and will stop receiving security updates near the end of March, 2019. Accordingly we need to upgrade to Ruby 2.4 or higher. Additionally, as Rails 3.2 is not supported on Ruby 2.4 or higher, we need to update to at least Rails 4.2.

[wwahammy]

I propose we do this for version 2.

[jenkijo]

I plan to use Houdini for my project, I think I can help you upgrade to Rails 6

[wwahammy]

@phongtruongg that's great! I have a partial Rails 5 upgrade done already at https://github.com/houdiniproject/houdini/tree/rails_v5. I'd love to coordinate with you on upgrade work. Would you be interested in meeting on our Zulip in the coming week?