Force symfony/yaml to ~2.7 since hassankhan/config depends on ~2.3 and is incompatible with ~3.0 (which phpunit would install).

Author: tomzx

composer.json

@@ -26,6 +26,7 @@
 		"herrera-io/phar-update": "~2.0",
 		"nikic/php-parser": "~1.3",
 		"symfony/console": "~2.7",
+		"symfony/yaml": "~2.7",
 		"tomzx/finder": "~0.1@dev"
 	},
 	"require-dev": {