Moving rails dependency as a dev one

[mustela]

There is no need to have a rails dependency, specially because it's requiring gems like we don't actually need on specific rails apps like APIs.

sprockets/railtie: 3.6641 MiB
      sprockets/rails/context: 2.1406 MiB
        action_view/helpers: 2.1406 MiB
          action_view/helpers/form_helper: 1.6328 MiB (Also required by: action_view/helpers/form_options_helper)
            action_view/helpers/form_tag_helper: 1.5547 MiB
              action_view/helpers/text_helper: 1.4219 MiB
                action_view/helpers/sanitize_helper: 1.4219 MiB
                  rails-html-sanitizer: 1.4219 MiB
                    loofah: 1.375 MiB
                      nokogiri: 1.1719 MiB
                        nokogiri/xml: 0.4063 MiB
                        nokogiri/html: 0.3672 MiB
      sprockets: 1.3672 MiB (Also required by: sprockets/rails/context, sprockets/rails/helper)
        sprockets/environment: 0.543 MiB
          sprockets/base: 0.5117 MiB (Also required by:

[andrerpbts]

Hello @mustela

Do you think you can adapt it to the new version?

I think Knock is currenlty strictly linked with Rails because the controllers/routes way. However your proposal seems to make the gem more lightweight, depending only of the rails installed in the project hosting that's Knock gem. Is that right?

Thank you!