## Thoughts

  * ~~strip hashes and everything following (as they're in-page anchors)~~
  * ~~strip args~~
  * ~~use `pop()` on the set instead of `.remove()`~~
    * ~~return false once the set is empty~~
  * ~~`WebPage.parse_urls()` needs to compare startswith to base url~~
  * ~~ignore any links which aren't to pages~~
  * ~~better url checking to get bare domain~~ #wontfix
  * ~~remove trailing slash from any discovered url~~
  * ~~investigate lxml parser~~
  * ~~remove base url from initial urls with and without trailing slash~~
  * ~~investigate using [tldextract](https://github.com/john-kurkowski/tldextract) to match urls~~ #wontfix
  * ~~implement parsing of [robots.txt](http://docs.w3cub.com/python~3.6/library/urllib.robotparser/)~~
  * ~~investigate [gzip encoding](https://stackoverflow.com/questions/36383227/avoid-downloading-images-using-beautifulsoup-and-urllib-request)~~
  * ~~implement some kind of progress display~~
  * async
  * better exception handling