Fix typos

See merge request lamp/cs-210-functional-programming-2019!7

# Conflicts:
#	slides/sources/progfun1-2-3.md
#	slides/sources/progfun1-2-5.md
#	slides/sources/progfun1-2-6.md
#	slides/sources/progfun1-2-7.md
#	slides/sources/progfun1-3-1.md
#	slides/sources/progfun1-3-2.md
#	slides/sources/progfun1-3-3.md
#	slides/sources/progfun1-3-4.md
#	slides/sources/progfun1-3-5.md
#	slides/sources/progfun1-4-1.md
#	slides/sources/progfun1-4-2.md
#	slides/sources/progfun1-4-3.md
#	slides/sources/progfun1-4-4.md
#	slides/sources/progfun1-4-5-decomposition.md
#	slides/sources/progfun1-4-5.md
#	slides/sources/progfun1-4-6-pattern-matching.md
#	slides/sources/progfun1-4-6.md

Otherwise install may fail if the index is out of date.

Fix links in repo outline

See merge request lamp/cs-210-functional-programming-2019!6

And use relative ones to make it portable

They start next Friday, the schedule was off by a week.

Fix missing code block for some scala code.

See merge request lamp/cs-210-functional-programming-2019!5