Converting to markdown.
Figures are all text.
First run through of copy editing for Chapter 6. Kincaid is 8.4, so it needs further work.
Simplified chaper 6 text
I have corrected/translated the first 3 python scripts:
- hello.py->hola.py
- guess.py->adivinaElNúmero.py
- dragon.py->dragón.py

I have also added placeholders for Spanish code scripts (e.g. "es_collisionDetection.py") that will be removed as the translated files (e.g. "detecciónDeColisiones.py") are added.

I need to check with Al whether he intends to translate the names of the additional files (e.g. "cherry.jpg" -> "cereza.jpg")
Renaming back to .txt. Markdown isn't a suitable format for this purpose.