add new api

db/migrate/20170208065307_create_product_types.rb

@@ -0,0 +1,7 @@
+class CreateProductTypes < ActiveRecord::Migration[5.0]
+  def change
+    create_table :product_types do |t|
+	    t.string    :name      
+    end
+  end
+end

db/migrate/20170208065316_create_product_categories.rb

@@ -0,0 +1,8 @@
+class CreateProductCategories < ActiveRecord::Migration[5.0]
+  def change
+    create_table :product_categories do |t|
+    	 t.string     :name  
+    	 t.references :product_type
+    end
+  end
+end