Update caching library to latest version, updated and fixed phpUnit tests

tests/OfflineTests/AccountGateway/AAUIDParserTest.php

@@ -8,7 +8,7 @@ namespace CloudObjects\SDK\AccountGateway;
 
 use ML\IRI\IRI;
 
-class AAUIDParserTest extends \PHPUnit_Framework_TestCase {
+class AAUIDParserTest extends \PHPUnit\Framework\TestCase {
 
   public function testValidAccountAAUID() {
     $aauid = new IRI('aauid:abcd1234abcd1234');