add db index for authentication_token column in users table

db/migrate/20130326142630_add_index_to_users_authentication_token.rb

+class AddIndexToUsersAuthenticationToken < ActiveRecord::Migration
+  def change
+    add_index :users, :authentication_token, unique: true
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20130614132337) do
+ActiveRecord::Schema.define(:version => 20130326142630) do
 
   create_table "deploy_keys_projects", :force => true do |t|
     t.integer  "deploy_key_id", :null => false
@@ -298,6 +298,7 @@ ActiveRecord::Schema.define(:version => 20130614132337) do
   end
 
   add_index "users", ["admin"], :name => "index_users_on_admin"
+  add_index "users", ["authentication_token"], :name => "index_users_on_authentication_token", :unique => true
   add_index "users", ["email"], :name => "index_users_on_email", :unique => true
   add_index "users", ["extern_uid", "provider"], :name => "index_users_on_extern_uid_and_provider", :unique => true
   add_index "users", ["name"], :name => "index_users_on_name"