NEW Added a few more learning algorithms to the example in the synthetic_data module.

Added SGD classifier, SGD classifier with grid search for the best alpha and k-NN learning algorithms.
NEW Added the k-NN and naive Bayes base learners to the testing configuration 50.
RESULT Added results of experiments on synthetic Boolean data with changing base learner (used k-NN and decision tree).
ENH Changed the parameters of the k-NN base learner and set the mode to "combine".