Added support for serialization to SequenceFileBolt

Added support for org.apache.hadoop.io.serializer.Serialization to the
SequenceFileBolt. The new SerializableSequenceFormat interface allows
serialization systems like Avro to be plugged into the SequenceFileBolt.
The new interface and type checking is only necessary for backwards compatibility, you could change the return type of original SequenceFormat interface to Object and no other code change will be necessary . I would add that as a comment here so when we decide to do a major version bump we could get rid of this extra code and the extra interface.