KAFKA-3216: "Modifying topics" section incorrectly says you can't change replication factor.

Correct the text that said that you can't change the replication factor of a topic.

Author: James Cheng <jylcheng@yahoo.com>

Reviewers: Ismael Juma

Closes #881 from wushujames/KAFKA-3216

docs/ops.html

@@ -62,7 +62,9 @@ And finally deleting a topic:
 Topic deletion option is disabled by default. To enable it set the server config
   <pre>delete.topic.enable=true</pre>
 <p>
-Kafka does not currently support reducing the number of partitions for a topic or changing the replication factor.
+Kafka does not currently support reducing the number of partitions for a topic.
+<p>
+Instructions for changing the replication factor of a topic can be found <a href="#basic_ops_increase_replication_factor">here</a>.
 
 <h4><a id="basic_ops_restarting" href="#basic_ops_restarting">Graceful shutdown</a></h4>