- After doing some extensive performance testing, I found no benefit to
  the 'pipelined lpop' implementation.

  Both implementations (batch evalsha vs pipelined lpop calls) perform
  exactly the same in my tests, but EVALSHA has the benefit of only
  doing one request to redis, where as pipelined lpop incurs N
  requests to redis, even if they are pipelined.

  As a result of similar performances, and EVALSHA having significantly
  less network chatter, I have decided to only support EVALSHA.

  This patch also removes the short-lived "pipeline_count" setting.

  The only option now is 'batch_count' to set how many items to fetch
  at a time.