Merge branch 'exercise_4' of gitlab.cs.ui.ac.id:pmpl/practice-collection/2019/1606889830-practice into exercise_4

# Conflicts:
#   README.md
#   functional_tests/tests.py
#   lists/static/home1.scss
#   lists/templates/homepage.html
#   lists/templates/list.html
#   superlists/settings.py

Exercise 4

See merge request !4

Exercise 3

See merge request !3

Exercise 2 [EDIT EXTERNAL DB & FORGOT SQUASH COMMIT]

See merge request !2

Exercise 2

See merge request !1