Bump jms/serializer-bundle from 2.4.3 to 3.0.1

Bit of a weird one, I think there's a bug in the upgrade instructions and have asked the maintainer to clarify (schmittjoh/serializer#1030).

Bumps [jms/serializer-bundle](https://github.com/schmittjoh/JMSSerializerBundle) from 2.4.3 to 3.0.1.
- [Release notes](https://github.com/schmittjoh/JMSSerializerBundle/releases)
- [Changelog](https://github.com/schmittjoh/JMSSerializerBundle/blob/master/CHANGELOG.md)
- [Commits](schmittjoh/JMSSerializerBundle@2.4.3...3.0.1)

app/config/config.yml

@@ -113,7 +113,7 @@ fos_rest:
 
 jms_serializer:
     visitors:
-        json:
+        json_serialization:
             options: JSON_PRETTY_PRINT
 
 acts_camdram:

composer.json

@@ -32,7 +32,7 @@
 		"friendsofsymfony/rest-bundle": "^2.3",
 		"hwi/oauth-bundle": "^0.6",
 		"incenteev/composer-parameter-handler": "^2.1",
-		"jms/serializer-bundle": "^2.4",
+		"jms/serializer-bundle": "^3.0",
 		"knplabs/github-api": "^2.8",
 		"liip/imagine-bundle": "~1.9",
 		"oneup/uploader-bundle": "^2.0",