bump AR dependency to ~> 4.0

paranoia.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.required_rubygems_version = ">= 1.3.6"
   s.rubyforge_project         = "paranoia"
 
-  s.add_dependency "activerecord", ">= 4.0.0.beta1"
+  s.add_dependency "activerecord", "~> 4.0"
 
   s.add_development_dependency "bundler", ">= 1.0.0"
   s.add_development_dependency "sqlite3"