Fix the testsuite

PHPUnit_MockObject is not able to mock methods using a typehint on an
undefined class. So mocking the ContainerBuilder with this library
requires having the ExpressionLanguage component.

Author: stof

composer.json

@@ -22,6 +22,9 @@
         "symfony/console": "~2.0",
         "willdurand/jsonp-callback-validator": "~1.0"
     },
+    "require-dev": {
+        "symfony/expression-language": "~2.4"
+    },
     "autoload": {
         "psr-4": { "FOS\\JsRoutingBundle\\": "" }
     },