current ng-newsletter link results in a 500 page. found an alternate link, but I suspect it is temporary until the newsletter fixes their 500, so we may not want to update the link. either way, this PR addresses #3400
* Remove dead link from free-programming-books-tr.md
* Change Django heading to same size as other headings
* Update link for Learning Deep Architectures
* revert django heading
* undo space add
* Remove dead link from free-programming-books-tr.md
* Change Django heading to same size as other headings
* Update dead links
* revert django heading level
django is a subheading because it's a Python framework - see the outline, and note the alphabetization.
* Update DirectX programming link
* Fix add-on development in Blender link
* Fix GTK+ link
* Update .NET regex link
* Update link
* Update link
* Update link
* Replace Google C++ style guide link
* Update link
* Update link
* Fix link
* Update link
* Fix link
* Fix link
* Fix link
* Fix link
* Update link
* Fix link
* Fix link
* Update link
* Update link
* Fix link
* Update link
* Fix link
* Fix link
* Fix link
* Update link
* Update link
* Fix link
* Update link
* Fix link
* Fix link
* Update link
* Fix link
* Fix link
* Update link
* Fix link
* Fix link
* Fix link
* Fix link
* Fix link
* Fix link
* Fix link
* Fix link
* Update link
* Update link
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* Update link
* Fix link
* Update link
* Fix link
* Update link
* Update link
* Fix link
* Fix link
* Fix link
* Update link
* Update link
* Replace link
* Fix link
* Update link
* Update link
* Update link
* Update link
* Update link
* Fix link
* Sort link
* Sort
* Update link
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* Update link
* Update link
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* Update link
* Update link
* Fix lint warnings
* Added the React.js Succinctly.
* Update free-programming-books.md
* Included the Flutter, Azure Functions and Elixir Succinctly.
* Added two more books under flutter.