Migrating away from SerializerBundle - a start

We needed to use the SerializerContext in our project which is why we decided to move to a more recent branch of Serializer. This ServiceProvider doesn't need the SerializerBundle anymore, since it doesn't use any of the events from the bundle.

I haven't done the separator thing thing either, since we don't use that.

So, maybe you could use this as a start to get starting with migrating to Serializer >= 0.11

I also had an issue with the test, but I don't know what is causing it. It seems that the cache dir is created OK, but when serializing, it cannot be accessed anymore:

```
There was 1 error:

1) JMS\Tests\SerializerServiceProvider\SerializerServiceProviderTest::testSerialize
file_put_contents(/tmp/SerializerServiceProviderTest/annotations/719d01dd571df344db6422dcf185064108676db1.cache.php): failed to open stream: No such file or directory
```