Create dataToMatrixFile.py

There are two systems of indexes for each user and for each item 
Because in the original file, uesr/item id is not consecutive
This may bring problem of empty colomne/row in matrix if we construct 
a matrix of dimension(max_user_id, max_item_id)

That's why the first thing we shoud do is to transfer user/item id to matrix index
and functions for reverse translation.