added php download of membershipments

vendor/illuminate/contracts/Support/Jsonable.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Illuminate\Contracts\Support;
+
+interface Jsonable
+{
+    /**
+     * Convert the object to its JSON representation.
+     *
+     * @param  int  $options
+     * @return string
+     */
+    public function toJson($options = 0);
+}