Allow Symfony Process ^3.0 and ^4.0

Author: tony-martin-aste

composer.json

@@ -4,7 +4,7 @@
   "version": "1.0.4",
   "require": {
     "php": ">=5.3.3",
-    "symfony/process": "^2.6"
+    "symfony/process": "^2.6 || ^3.0 || ^4.0"
   },
   "autoload": {
     "psr-4": {