"Perceptron" is a "Learner", which has a method called "Learn".
"(*Perceptron).Learn" apply "(*Perceptron).learnInstance" to all instances.
"(*Perceptron).Learn" applies "(*Perceptron).learnInstance" to all instances and repeats N times (N is a "iteration").
"(*Perceptron).learnInstance" tries to infer the label. If it fails, perceptron updates the weight of inferencer.
Merge branch 'feature/interface'