Fix symfony/intl version

Author: bruli

composer.json

@@ -11,7 +11,7 @@
     "require": {
         "php": ">=5.6",
         "beberlei/assert": "^2.5",
-        "symfony/intl": "^3.1"
+        "symfony/intl": "~2.8|~3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.4",