fix error

announcement.gemspec

@@ -1,6 +1,5 @@
 # encoding: UTF-8
 $:.push File.expand_path("../lib", __FILE__)
-$:.push File.expand_path("../app/models", __FILE__)
 # Maintain your gem's version:
 require "announcement/version"
 require 'json'
@@ -294,7 +293,7 @@ Gem::Specification.new do |s|
   s.description = "Announcements for Orbit"
   s.license     = "MIT"
   s.metadata = {
-    "_require" => "announcement_setting",
+    "_require" => "#{File.expand_path("../app/models/announcement_setting", __FILE__)}",
     "global_hash" => "{enable_manually_sort: (AnnouncementSetting.first.enable_manually_sort rescue false)}"
   }
   s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]