added random_bytes support

auto merge accidentally removed this dependency

composer.json

@@ -12,7 +12,8 @@
     ],
     "require": {
         "php": ">=5.6",
-        "symfony/serializer": "~2.7|~3.0"
+        "symfony/serializer": "~2.7|~3.0",
+        "paragonie/random_compat": "^2.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~5.6",