Shouldn't the directive here be platforms??

Gemfile

@@ -11,19 +11,19 @@ gem "rake", Gem::Version.new(RUBY_VERSION) < Gem::Version.new("1.9.3") ? "~>10.3
 group :test do
   gem "rspec", ">= 3.2"
   # Older versions of some gems required for Ruby 1.8.7 support
-  platform :ruby_18 do
+  platforms :ruby_18 do
     gem "activesupport", "~> 3.2.21"
     gem "i18n", "~> 0.6.11"
   end
-  platform :ruby_18, :ruby_19 do
+  platforms :ruby_18, :ruby_19 do
     gem "mime-types", "~> 1.25"
     gem "json", "~> 1.8"
     gem "addressable", "~> 2.3.0"
   end
-  platform :ruby_18, :ruby_19, :ruby_20, :ruby_21 do
+  platforms :ruby_18, :ruby_19, :ruby_20, :ruby_21 do
     gem "rack", "~> 1.6"
   end
-  platform :jruby, :ruby_19, :ruby_20, :ruby_21, :ruby_22, :ruby_23 do
+  platforms :jruby, :ruby_19, :ruby_20, :ruby_21, :ruby_22, :ruby_23 do
     gem "aruba", "~> 0.7.4"
     gem "capybara"
     gem "cucumber"