msgpack_rails.gemspec in msgpack_rails-0.3.0 vs msgpack_rails.gemspec in msgpack_rails-0.4.0

@@ -22,6 +22,10 @@
   if RUBY_ENGINE == "jruby"
     spec.add_runtime_dependency "msgpack-jruby"
   else
     spec.add_runtime_dependency "msgpack"
   end
+
+  spec.add_development_dependency "rake", "~> 10.3.1"
+  spec.add_development_dependency "minitest", "~> 5.3.3"
+  spec.add_development_dependency "activemodel", "~> 4.1.0"
 end