Modified track_version.py (to import models)
Fix typo in internal/dev_start_guide.txt
Fix typo in config/yaml_parse.py
Fix docstrings in costs
Modify docstrings for a few datasets

Up to "Matlab Dataset"
Modify docstrings

From norb to zca_dataset
Modify 'retina.py'

Should we modify how the parameters are shown?
Modify docstrings in datasets : Other
Revert track_version.py to original state
Reduce line length
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?
Remove trailing whitespace
Update svhn
Revert track_version.py to original state
Replace tabs by spaces
Revert "Replace tabs by spaces"

This reverts commit 1f4a9e6b31d2d6c49bcbc9c66392dbbd4aab662e.
Merge pull request #704 from sebastien-j/issue-372-up-to-datasets

#372: Fixes docstrings for files under

config/
costs/
datasets/