FLUME-2723 batch size trans cap doc update
FLUME-2723 batch size trans cap doc update

An update to the configuration section of the user guide.

This closes #246

Reviewers: Peret Turcsanyi, Ferenc Szabo

(Endre Major via Ferenc Szabo)

tmgstevens/flume,tmgstevens/flume,szaboferee/flume,szaboferee/flume,szaboferee/flume,tmgstevens/flume,szaboferee/flume,tmgstevens/flume