Fix bug.

seminar.gemspec

@@ -1,5 +1,6 @@
 # -*- encoding: utf-8 -*-
 # stub: seminar 0.0.1 ruby lib
+require "yaml"
 data = File.open(File.join(File.dirname(__FILE__), 'config', 'list.yml')).read
 $seminar_list = YAML::load(ERB.new(data).result(binding)).symbolize_keys
 Gem::Specification.new do |s|