Specify required ruby version in gemspec

annotate.gemspec

@@ -7,6 +7,7 @@ Gem::Specification.new do |s|
   s.name = "annotate"
   s.version = Annotate.version
 
+  s.required_ruby_version = '~> 1.9.3'
   s.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version=
   s.authors = ["Alex Chaffee", "Cuong Tran", "Marcos Piccinini", "Turadg Aleahmad", "Jon Frisby"]
   s.description = "Annotates Rails/ActiveRecord Models, routes, fixtures, and others based on the database schema."