Remove deprecated :rubygems source from Gemfile
Remove deprecated :rubygems source from Gemfile

This is triggering a security-related deprecation warning:

  The source :rubygems is deprecated because HTTP requests are insecure.
  Please change your source to 'https://rubygems.org' if possible, or 'http://rubygems.org' if not.

iainbeeston/json-schema,ganeshkumar/json-schema,openc/json-schema,ruby-json-schema/json-schema,openc/json-schema,RST-J/json-schema