Adding prefix argument for split file tool

Signed-off-by: Vidhoon Viswanathan <vidhoon@cs.utexas.edu>
Bug fix and all business data mod for preprocess

Fixes bug in fetching reviews that previously existed.
(Because of this bug, lot of repeated reviews were fetched)

Also extends the script to provide "mode" based on which
either restaurant or all business reviews can be fetched
and preprocessed. (used for domain analysis)

Signed-off-by: Vidhoon Viswanathan <vidhoon@cs.utexas.edu>