Support to create topic

[psalot]

I am using this library but I want to enable creating topics from code as we have in node-rdkafka
https://github.com/Blizzard/node-rdkafka#admin-client

can you enable this?
This will help in creating topics at the runtime
I think all that needs to be done here is expose the Adminclient object as is from the KafkaAvro as below in the file lib/kafka-avro.js

[ricardohbin]

this lib has focus schema-registry (with pre-created topics following a standard). Expose the entire AdminClient just to create topics in runtime not fit well to the purpose of this lib. What do you think?