FEATURE: Can create warnings for users via PM

db/migrate/20140905171733_create_warnings.rb

@@ -0,0 +1,12 @@
+class CreateWarnings < ActiveRecord::Migration
+  def change
+    create_table :warnings do |t|
+      t.references :topic, null: false
+      t.references :user, null: false
+      t.integer :created_by_id, null: false
+      t.timestamps
+    end
+    add_index :warnings, :user_id
+    add_index :warnings, :topic_id, unique: true
+  end
+end