Correct income_classifier.py

[alxnkt]

Fix issue about using LabelEncoder.transform and np.array functions, as they accept only arrays.

[RahulVadisetty91]

The cross_validation module has been deprecated and replaced with model_selection in the newer versions of scikit-learn.

from sklearn.model_selection import train_test_split, cross_val_score

Update all instances of cross_validation to model_selection, like this:

X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=5)
f1 = cross_val_score(classifier, X, y, scoring='f1_weighted', cv=3)