- Rearranged the big blocks to be in a logical order rather than alphabetical order. Walker > Downloader > other classes
- Renamed the `keep_pattern` and `remove_pattern` functions to `keep_pattern_argparse` etc to be consistent with the other functions that take argparse namespaces as their only parameter. Does not affect the commandline usage.
- Gave the HTML tree divs a very gentle shadow and alternating colors to help with depth perception.