Added ClassifierMixin and MetaEstimatorMixin to super classes
Modifications to the class parameter documentation. Added default values and types.
No need to implement get_params and set_params, since this is already implemented in BaseEstimator
Removed self.c=1 from constructor
Removed useless exception
TODOs and sklearn style comments for methods
predict returns an np.array
Less generic error message when not fitted in prediction methods
Merge pull request #2 from aldro61/pulearning

Completed a few TODOs