- **[change]** Moved some nested function definitions out to the top level, and made the construction of the file tree its own function. These functions really don't need to be used on their own, but they were cluttering the logic of the `tree` command.
- **[change]** Renamed `Tree.listnodes` to `Tree.list_children`, and the `customsort` now expects to operate on Node objects rather than `(identifier, Node)` tuples. Nodes already have their identifier so the tuple was unecessary.
- **[change]** Replaced local `download_file` function with a call to `downloady.download_file`. It supports download continuation and removes duplicate work.
- **[cleanup]** Replaced all `safeprint` calls with `write` because it provides access to safeprint as well as file writing if needed.
- **[removal]** Removed `Tree.sorted_children` since it was basically a duplicate of `Tree.listnodes` and I don't know why I had both.
- **[addition]** Gave the HTML tree divs a very gentle shadow and alternating colors to help with depth perception.
- **[bugfix]** Fixed the allowed characters parameter of `filepath_sanitize`, which was not written correctly but worked out of luck.
- **[cleanup]** Rearranged the big blocks to be in a logical order rather than alphabetical order. Walker > Downloader > other classes
- **[cleanup]** Renamed the `keep_pattern` and `remove_pattern` functions to `keep_pattern_argparse` etc to be consistent with the other functions used by the argparser. *Does not affect the commandline usage!*
- **[cleanup]** Fixed some mismatched code vs comments
