Merge pull request rspec#2747 from rspec/avoid-security-warning

Lock minimum json version

Author: JonRowe

Gemfile

@@ -36,6 +36,8 @@ end
 
 if RUBY_VERSION < '2.0.0' || RUBY_ENGINE == 'java'
   gem 'json', '< 2.0.0'
+else
+  gem 'json', '> 2.3.0'
 end
 
 if RUBY_VERSION < '2.2.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)