Ruby on Rails incompatible library

I had a similar problem to what you described after I had taken a different ruby version into use (from 2.3.0 -> 2.3.3).

I found that running:

$ gem install bundler

Then:

$ bundle install

... worked a charm for me. This reinstalled all of the packages I needed in my Gemfile without any dependency issues.

Remove vendor and run bundle install could solve this problem. It worked for me.

Something's gotten weird/corrupted in your ruby environment. I'd blame rvm. Personally I am not a fan of rvm.

But you might try gem uninstall json, follow prompts to uninstall ALL versions. Then bundle install again. Then hopefully you'll be fixed up.