Adopt dependency for PHP 7.3

It is risky to overwrite the platform version, but now seems to work normally.

Author: zonuexe

composer.json

@@ -23,6 +23,9 @@
     "config": {
         "optimize-autoloader": true,
         "classmap-authoritative": true,
-        "sort-packages": true
+        "sort-packages": true,
+        "platform": {
+            "php": "7.1.3"
+        }
     }
 }