Add usage hint for cglib, joda datetime and wicket minimap serializers to README.
Add usage hint for cglib, joda datetime and wicket minimap serializers to README.

relateiq/kryo-serializers,Crim/kryo-serializers,magro/kryo-serializers,psmarcos/kryo-serializers,aaronpoweruser/kryo-serializers,fgaule/kryo-serializers