fix: ensure latest version of rack is used to avoid vulnerability CVE-2018-16471

Author: bethesque

pact_broker.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency 'sequel', '~> 5.6'
   gem.add_runtime_dependency 'webmachine', '1.5.0'
   gem.add_runtime_dependency 'semver2', '~> 3.4.2'
-  gem.add_runtime_dependency 'rack', '~>2.0'
+  gem.add_runtime_dependency 'rack', '>= 2.0.6', '~>2.0'
   gem.add_runtime_dependency 'redcarpet', '>=3.3.2', '~>3.3'
   gem.add_runtime_dependency 'pact-support'
   gem.add_runtime_dependency 'padrino-core', '>= 0.14.3', '~> 0.14'