Templates: We Live, We Learn

Some lesson source is executable, such as R Markdown files or IPython Notebooks. If we put those in a sub-directory called pages, they have to refer to external data files and images as ../data/datafile.csv and ../img/image.png. When we compile them to create HTML pages in the root directory, though, those paths need to change, which adds a post-processing step we'd rather not have to build and maintain.
Novice contributors find the flatter structure with unchanging file paths easier to understand, in part because it more closely mirrors the way a researcher would lay out one of her papers.

A pull request to make this change is under review right now; we hope to merge it later today, and then patch the partially-translated lessons to match by the end of the week. I hope this will be the last big change to the template; if nothing else, the past few weeks have illustrated two core rules of engineering:

There's no such thing as right and wrong: there's only better and worse. Putting generated files in the same directory as source files is generally a bad idea, but in this case, the pros outweigh the cons.
The only way to tell if something works is to build it. We have a lot of experience writing lessons, and put a lot of thought into the new templates. We still made the wrong call on this aspect of layout, but I don't feel bad about that: if we get 90% of things right, 90% of the time, we're doing pretty well.