Bump minimum Symfony version to last LTS (2.7)

moux2003 · moux2003 · commit ba6642846bf3 · 2018-02-18T17:52:14.000+01:00
diff --git a/composer.json b/composer.json
@@ -11,7 +11,7 @@
   ],
   "require": {
     "php": ">=5.4",
-    "symfony/symfony": ">=2.5",
+    "symfony/symfony": ">=2.7",
     "sendgrid/sendgrid": "^5.0"
   },
   "autoload": {
