Numbered the chapter folders so that they're listed in order.

[bmispelon]

I grew tired of constantly referring to SUMMARY.md to figure out the order of the chapters and decided to bite the bullet.

I used the following renames:

git mv {,01_}how_internet_works
git mv {,02_}intro_to_command_line/
git mv {,03_}python_installation/
git mv {,04_}python_introduction/
git mv {,05_}django
git mv {,06_}django_installation/
git mv {,07_}code_editor/
git mv {,08_}django_start_project/
git mv {,09_}django_models/
git mv {,10_}django_orm/
git mv {,11_}django_admin/
git mv {,12_}deploy/
git mv {,13_}django_urls/
git mv {,14_}django_views/
git mv {,15_}html
git mv {,16_}dynamic_data_in_templates/
git mv {,17_}django_templates
git mv {,18_}css
git mv {,19_}template_extending/
git mv {,20_}extend_your_application/
git mv {,21_}django_forms
git mv {,22_}domain
git mv {,23_}whats_next/

And fixed the few links in some of the chapters (found with git grep README).

[keikoro]

Ahh! What I've been meaning to change for the longest time is the name of the first chapter, which should read "how the internet works" (or, alternatively/when asked as a question, "how does the internet work").

[bmispelon]

Come to think of it, this might create some broken links if people have linked to specific chapters directly :(

I'm not sure if there's a way to fix that. Maybe a gitbook plugin to add redirects?

[olasitarska]

@bmispelon I think it's best to do it now and don't worry too much about broken links.

[bmispelon]

I've rebased the pull request on top of the latest master and added a commit to rename the first chapter as per @kerstin 's suggestion.

[keikoro]

Coolio! 🍬

[olasitarska]

Giving the current number of headaches this change would gave us, I am just going to close this PR. Ok @bmispelon ?