faster build.

Test only supported version of rails.
Test in Rails 5.0

google-api-client.gemspec

@@ -27,5 +27,5 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'googleauth', '~> 0.5'
   spec.add_runtime_dependency 'httpclient', '>= 2.8.1', '< 3.0'
   spec.add_development_dependency 'thor', '~> 0.14'
-  spec.add_development_dependency 'activesupport', '>= 3.2', '< 5.0'
+  spec.add_development_dependency 'activesupport', '>= 4.2', '< 5.1'
 end