Add trailing final newlines to source files.

Touched a ton of files to finally standardize on having trailing
final newlines, as best practice recommends and so our devs stop
accidentally fighting each other over it.

This was performed automatically with the following:
git ls-files -z '*.py' | while IFS= read -rd '' f; \
    do tail -c1 < "$f" | read -r _ || echo >> "$f"; done
git ls-files -z '*.css' | while IFS= read -rd '' f; \
    do tail -c1 < "$f" | read -r _ || echo >> "$f"; done

files/__init__.py

@@ -0,0 +1 @@
+