symfony version bump

Author: janxb

composer.json

@@ -5,6 +5,7 @@
     "php": "^7.1.3",
     "ext-ctype": "*",
     "ext-iconv": "*",
+    "psr/simple-cache": "*",
     "incenteev/composer-parameter-handler": "^2.1",
     "johngrogg/ics-parser": "^2.1",
     "sensio/framework-extra-bundle": "^5.1",
@@ -84,7 +85,7 @@
   "extra": {
     "symfony": {
       "allow-contrib": false,
-      "require": "4.1.*"
+      "require": "4.3.*"
     },
     "incenteev-parameters": {
       "file": "config/parameters.yaml"