Update the composer require section

Update the composer require section to fit with doctrine/migration's new
builFromSql method, starting by v1.4

composer.json

@@ -9,6 +9,6 @@
         "php": ">=5.4.0",
         "symfony/framework-bundle": "~2.3|~3.0",
         "doctrine/doctrine-bundle": "~1.0",
-        "doctrine/migrations": "~1.0"
+        "doctrine/migrations": "~1.4"
     }
 }