added post voting

db/migrate/20100215223541_create_post_votes.rb

@@ -0,0 +1,13 @@
+class CreatePostVotes < ActiveRecord::Migration
+  def self.up
+    create_table :post_votes do |t|
+      t.column :post_id, :integer, :null => false
+      t.column :user_id, :integer, :null => false
+      t.timestamps
+    end
+  end
+
+  def self.down
+    drop_table :post_votes
+  end
+end