Dependency on google_visualr 2.5.1 is broken

[Andrew-Max]

As noted here: winston/google_visualr#118

google_visualr 2.5.1 is broken and the maintainer of that project will not merge PRs with fixes

This manifests as

 undefined method `helper_method' for ActionController::API:Class (NoMethodError)

        helper_method "render_chart"

Someone else has forked that project and created a tagged fix

https://rubygems.org/gems/google_visualr_rails5

Would it be possible to switch the dependency to this gem?

[Andrew-Max]

#169