Large update for version 2.0

src/Contracts/Buyable.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace Gloudemans\Shoppingcart\Contracts;
+
+interface Buyable
+{
+    /**
+     * Get the identifier of the Buyable item.
+     *
+     * @return int|string
+     */
+    public function getBuyableIdentifier();
+
+    /**
+     * Get the description or title of the Buyable item.
+     *
+     * @return string
+     */
+    public function getBuyableDescription();
+
+    /**
+     * Get the price of the Buyable item.
+     *
+     * @return float
+     */
+    public function getBuyablePrice();
+}