Generate reposts model/table that stores the repost history.

db/migrate/20131208115327_create_reposts.rb

@@ -0,0 +1,12 @@
+class CreateReposts < ActiveRecord::Migration
+  def change
+    create_table :reposts do |t|
+      t.string :mentioned
+      t.bigint :postid
+      t.bigint :repostid
+
+      t.timestamps
+    end
+    add_index :reposts, :repostid
+  end
+end