class BundlerVendoredPostIt::PostIt::Installer

def installed?
  if Gem::Specification.respond_to?(:find_by_name)
    !Gem::Specification.find_by_name('bundler', @bundler_version).nil?
  else
    requirement = Gem::Requirement.new(@bundler_version)
    Gem.source_index.gems.values.any? do |s|
      s.name == 'bundler' && requirement.satisfied_by?(s.version)
    end
  end
rescue LoadError
  false
end