WIP: adds "paths-and-directories" and "concurrent-processes" examples

[friedbrice]

• working with paths and directories
• concurrently working with processes

This is marked as WIP because it has a few problems:

1. How to (or is it even a good idea to) import files from a previous lesson.
2. Perhaps it's too complicated or too specific.
3. I don't like that it applies a record update on CreateProcess without introducing CreateProcess first.
4. Since it deals with files we're not creating, the results are sensitive to the user's environment.

[friedbrice]

Addresses issue: https://github.com/typeclasses/haskell-phrasebook/issues/22