Require Ruby 1.9.3 or higher

Author: AndrewJo

green-button-data.gemspec

@@ -15,7 +15,8 @@ Gem::Specification.new do |s|
   s.files         = `git ls-files`.split("\n")
   s.require_paths = ['lib']
 
-  s.platform    = Gem::Platform::RUBY
+  s.platform              = Gem::Platform::RUBY
+  s.required_ruby_version = '>= 1.9.3'
 
   s.add_dependency 'nokogiri', '~> 1.6'
   s.add_dependency 'sax-machine', '~> 1.3'