atoum update

Author: Olivier Mansour

composer.json

@@ -12,7 +12,7 @@
         "php": ">=5.4.0"
     },
     "require-dev": {
-        "atoum/atoum": "~1.0",
+        "atoum/atoum": "~2.0",
         "m6web/symfony2-coding-standard": "~1.2",
         "m6web/coke": "~1.2"
     },