Neural networks update

See merge request sis/courses/machinelearning-introduction-workshop!38

Merge branch '26-add-images-data-classification-w-svm-and-squeeze-out-a-lot-of-performance' into 'master'

Resolve "Add images data classification w/ SVM and squeeze out a lot of performance"

Closes #26

See merge request sis/courses/machinelearning-introduction-workshop!49

- Fix checks if setup works on windows.
- Restructure content because based on the fix for Windows the previous instructions layout became to complex.

Resolve "Include images for PCA"

Closes #47

See merge request sis/courses/machinelearning-introduction-workshop!48

Resolve "Fix or remove comment on out-of-bag-error for Random Forests"

Closes #44

See merge request sis/courses/machinelearning-introduction-workshop!45

Resolve "Update installation instructions"

Closes #50

See merge request sis/courses/machinelearning-introduction-workshop!47

Resolve "Validation data in the time series regression"

Closes #57

See merge request sis/courses/machinelearning-introduction-workshop!44

# Conflicts:
#   07_regression.ipynb

Resolve "Clarify scaling description and pipelines"

Closes #46

See merge request sis/courses/machinelearning-introduction-workshop!43

# Conflicts:
#   CONTRIBUTING.md