Lock Rack version to < 2 (no longer supports Mongrel) (#328)

Author: CodeMonkeySteve

em-http-request.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency 'mongrel', '~> 1.2.0.pre2'
   s.add_development_dependency 'multi_json'
-  s.add_development_dependency 'rack'
+  s.add_development_dependency 'rack', '< 2.0'
   s.add_development_dependency 'rake'
   s.add_development_dependency 'rspec'