Fix Behatch constraint

Author: dunglas

composer.json

@@ -31,7 +31,7 @@
         "behat/mink-browserkit-driver": "^1.3.1",
         "behat/mink-extension": "^2.2",
         "behat/symfony2-extension": "^2.1.1",
-        "behatch/contexts": "3.1.0",
+        "behatch/contexts": "^3.1.0",
         "doctrine/annotations": "^1.7",
         "doctrine/common": "^2.11",
         "doctrine/data-fixtures": "^1.2.2",