Removed tabs in django_orm chapter.

There shouldn't be any left now.
Removed trailing whitespace and empty lines in django_orm chapter.
Pep8-ified the examples in django_orm chapter.
Removed unnecessary .all() calls in django_orm chapter.
New Gitbook covers
Merge pull request #118 from bmispelon/orm-chapter

A few fixes for the ORM chapter
Numbered the chapter folders so that they're listed in order.
Renamed the 'How the Internet works' chapter.

Thanks to @kerstin for the suggestion.