Replace Light Table with PyCharm

Light Table seems to cause lot of confusion for newbies, I don't think PyCharm is necessarily
easier but I don't see a better alternative.

Also, PyCharm is more likely to be around, now that Light Table is deprioritized by the creators:
http://www.chris-granger.com/2014/10/01/beyond-light-table/
Add function to upload output formats
Removing defunct comment
Add feedback by myd7349
Mention course at University of Ljubljana Slovenia
Add last-updated-at timestamp
Move last-updated-at to Preface chapter
Simplifying Emacs recommendations
Simplify sentences in Python 2 vs. 3 section