Fit multivariate normal for outlier detection

Add polylearn dependency

Fix bug in computing decision boundary

Bestter explain usage of GMM for outlier detection

Exercise 8 - Anomaly detection and recommender systems

Exercise 7 - K-means clustering and principal component analysis

Replace wrong usage of term sample with example

Better settings for displaying handwritten digits

Use term test set instead of validation set in context of CV

Exercise 6 - Support vector machines

Add test scores to polynomial regression example

Minor edits in README

Fix title in exercise 4 notebook

Add not-yet completed exercises to README

Exercise 5 enhancements