Add max_number_of_messages parameter

Add `max_number_of_messages` parameter to control maximum number of messages to receive.
Tuning this parameter can be improve message fetch performance.

This parameter is optional, and default value is not changed. So current user does not have to change their configuration.

http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/SQS/Queue.html#receive_message-instance_method