require 5.4 and add JsonSerializable

.gitignore

@@ -1,3 +1,4 @@
+.idea/
 *.phar
 .DS_Store
 build

composer.json

@@ -20,7 +20,7 @@
         "source": "https://github.com/ramsey/uuid"
     },
     "require": {
-        "php": ">=5.3.3"
+        "php": ">=5.4"
     },
     "require-dev": {
         "moontoast/math": "~1.1",

src/Uuid.php

@@ -29,7 +29,7 @@ use InvalidArgumentException;
  * @link http://docs.python.org/3/library/uuid.html
  * @link http://docs.oracle.com/javase/6/docs/api/java/util/UUID.html
  */
-final class Uuid
+final class Uuid implements \JsonSerializable
 {
     /**
      * When this namespace is specified, the name string is a fully-qualified domain name.
@@ -175,6 +175,19 @@ final class Uuid
         return $this->toString();
     }
 
+    /**
+     * Converts this UUID object to a string when the object is serialized
+     * with json_encode()
+     *
+     * @link http://php.net/manual/en/class.jsonserializable.php
+     *
+     * @return string
+     */
+    public function jsonSerialize()
+    {
+        return $this->toString();
+    }
+
     /**
      * Compares this UUID with the specified UUID.
      *