MemoryError check

On tests (after setting max size to 15 bytes):

WARNING:kafka:Fetch size too small, increase to 2 (2x) and retry
WARNING:kafka:Fetch size too small, increase to 4 (2x) and retry
WARNING:kafka:Fetch size too small, increase to 8 (2x) and retry
ERROR:kafka:Message size exceeded maximum allowed of 15
ERROR:kafka:Current buffer_size is: 16
ERROR:kafka:topic: activity.stream, partition: 0, offset:24
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threading.py", line 763, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/Users/jjohn/dev/lfdemux/env/lib/python2.7/site-packages/kafka/consumer.py", line 436, in _fetch_loop
    self._fetch()
  File "/Users/jjohn/dev/lfdemux/env/lib/python2.7/site-packages/kafka/consumer.py", line 489, in _fetch
    raise MessageTooLargeError
MessageTooLargeError
See: 
https://github.com/Livefyre/kafka-python/blob/rm_kafka_memory_check/kafka/consumer.py#L384