updating development deps in gemspec

ipaddress.gemspec

@@ -21,6 +21,6 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.6"
-  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency "bundler"
+  spec.add_development_dependency "rake"
 end