Improved speed of LocalClassifier.predict by calling classifier.predict once with all cells.

* Added timing prints for train and test in LocalClassifier
* Consolidated calls to classifier.predict in LocalClassifier.predict into 1 call, much, much faster.
Added parameter to print performance for each delta in Classifier.test.
Added __str__ functions for nice object printing for ConwayBoard and Example classes.
Added load_examples to read examples from .csv in Kaggle format.
Implemented transformations of the feature representation for LocalClassifier to be used in training.

* Added transform argument to LocalClassifier._make_features that creates the features as if the board were in one of the 8 possible rotations/flips.
* Added use_transformations argument to LocalClassifier.train to use all transformations of boards when training.