Add PHP Code Sniffer to dev dependencies

src/composer.json

@@ -24,6 +24,9 @@
         "symfony/config": "2.4.*",
         "symfony/yaml": "2.4.*"
     },
+    "require-dev": {
+        "squizlabs/php_codesniffer": "1.*"
+    },
     "config": {
         "vendor-dir": "mibew/vendor"
     }