Implementation of cross_validation_wrapper.

Improvements, corrections and tests for games.py

Get branch even with latest changes in master

# Conflicts:
#	tests/test_utils.py
#	utils.py

Revised Implementation of backpropagation, util func

Improved test for and_or_search

Remove count_if, find_if, every, some, Struct; replace them with modern
Python equivalents.

Resolved conflicts in #125

Renamed run to __call__ for Online DFS Agent

Fix flake8 warnings

Fixed alphabeta_search