Update composer.json

Update requirement for zend-mime to 2.2.*

Author: calumbrodie

composer.json

@@ -26,7 +26,7 @@
         "ass/xmlsecurity": "~1.0",
         "symfony/framework-bundle": "~2.0",
         "symfony/twig-bundle": "~2.0",
-        "zendframework/zend-mime": "2.1.*"
+        "zendframework/zend-mime": "2.2.*"
     },
     "replace": {
         "besimple/soap-bundle": "self.version",