Require ruby 2.0 for Module#prepend

paranoia.gemspec

@@ -14,6 +14,8 @@ Gem::Specification.new do |s|
   s.required_rubygems_version = ">= 1.3.6"
   s.rubyforge_project         = "paranoia"
 
+  s.required_ruby_version = '>= 2.0'
+
   s.add_dependency "activerecord", "~> 4.0"
 
   s.add_development_dependency "bundler", ">= 1.0.0"