Format doc in binarizer.py and preprocessing.py

This commit adresses the comments made by @dwf in pull request #704.
Some additional modifications were also made.

Just to be sure :
1. Is the seed in class Binarizer an integer or a list of integers?
2.  Is the previous description of __init__() in class ShuffleAndSplit
(in preprocessor.py) applicable to the class itself?