Large Kafka Message Volume Causes OOME in CC-Pages

Issue Summary

When there is a large number of messages in Kafka, cc-pages will load all messages and run out of memory

Steps to Reproduce

1. Stop cc-pages from consuming messages from kafka.
2. Add a large number of messages to the doc proc topic in kafka.
3. Resume cc-pages consuming from kafka.

Expected Results

CC-Pages should consume messages at a rate that does not cause it to run out of memory. 

Actual Results

CC-Pages runs out of memory.

Workaround

Empty Kafka topic backlog causing OOME.