lock mspt to 21

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>

Author: ArtificialOwl

composer.json

@@ -20,6 +20,6 @@
     }
   },
   "require": {
-    "daita/my-small-php-tools": "dev-master"
+    "daita/my-small-php-tools": "~21"
   }
 }