add alias name to farge_activitiy index

db/migrate/20160324074942_add_index_to_forge_activities.rb

@@ -1,5 +1,5 @@
 class AddIndexToForgeActivities < ActiveRecord::Migration
   def change
-    add_index :forge_activities, [:project_id, :forge_act_id, :created_at]
+    add_index :forge_activities, [:project_id, :forge_act_id, :created_at], :name => 'forge_cat_project_id'
   end
 end