TODO: Get `avconv` working. Oftentimes `play` won't be able to play
      some tracks due to an unsupported format; we'll need to use
      `avconv` to convert them (to WAV).
      (Done!)

TODO: Get `play` working.
      (Done!)

TODO: Get play-next working; probably just act like a shuffle. Will
      need to keep an eye out for the `play` process finishing.
      (Done!)

TODO: Preemptively download and process the next track, while the
      current one is playing, to eliminate the silent time between
      tracks.
      (Done!)

TODO: Delete old tracks! Since we aren't overwriting files, we
      need to manually delete files once we're done with them.
      (Done!)

TODO: Get library filter path from stdin.
      (Done!)

TODO: Show library tree. Do this AFTER filtering, so that people
      can e.g. see all albums by a specific artist.
      (Done!)

TODO: Ignore .DS_Store.
      (Done!)

TODO: Have a download timeout, somehow.

TODO: Fix the actual group format. Often times we get single-letter
      files being downloaded (which don't exist); I'm guessing that's
      related to folder names (which are just strings, not title-href
      arrays) still being in the group array. (Update: that's defin-
      itely true; 'Saucey Sounds'[0] === 'S', and 'Unofficial'[0]
      === 'U', which are the two "files" it crashes on while playing
      -g 'Jake Chudnow'.)
      (Done!)

TODO: A way to exclude a specific group path.
      (Done!)

TODO: Better argv handling.
      (Done!)

TODO: Option to include a specific path from the source playlist.
      (Done!)

TODO: Make a playlist generator that parses http://billwurtz.com
      instrumentals.html.
      (Done!)

TODO: Make crawl-itunes.js a bit more general, more command-line
      friendly (i.e. don't require editing the script itself), and
      make it use the getHTMLLinks function defined in the new
      crawl-links.js script.
      (Done!)

TODO: Play-in-order track picker.
      (Done!)

TODO: Volume controls. Who knows how to do this? It might have to be an
      argument passed to `play`. Being able to change the volume while it's
      playing would be nice, but I'm not sure if that's really possible.
      (Done! - To the greatest current ability.)

TODO: Tempfiles, maybe?
      (Done!)

TODO: Use NOT the internet as its source, so that it's a bit more general
      purpose. This would only take adding a new downloader.
      (Done!)

TODO: Recursive local file playlist crawler.
      (Done!)

TODO: *Requiring* a literal `playlist.json` file doesn't seem quite right,
      especially since there's the `--open` option.
      (Done!)

TODO: Make local downlaoder sort more natural - that is, 10 comes immediately
      after 9, not 1. (1, 5, 9, 10, 12; not 1, 10, 12, 5, 9.)
      (Done!)

TODO: Make a way to skip tracks while playing. Currently the only way is to
      kill and restart the http-music process; this is bad for numerous
      reasons, particularly because it gets rid of the pre-downloaded track and
      forces the user to wait for another one to be downloaded.
      (Done!)

TODO: Make a --help/-h/-? option that directs helpless users to the man page.
      (Done!)

TODO: Make a way to write the current playlist to a file. I think just renaming
      the debug-playlist-log option could work, since you could pipe that to a
      file through your shell.

TODO: Figure out a less "hacky" way to kill the process. Ideally we shouldn't
      have to handle ^C and ^D ourselves; for instance right now ^Z is actually
      broken, since we aren't using the shell's normal way of handling any
      keyboard controls such as those!

TODO: Separate the code in loop-play.js to be a bit nicer.
      (Done!)

TODO: Cleaning up http-music.js would be nice as well!

TODO: A way to kill the up-next song.
      (Done!)

TODO: A way to see information about the currently playing song, as well as
      the up-next song.

TODO: A way to see the previously played songs, and to skip back (or forwards).

TODO: Exit on loop-play end. (Since it listens to stdin for input right now,
      it won't automatically stop.)

TODO: Figure out how to attempt to avoid being forced to convert every file..
      converting a 10MB MP3 into an 80MB WAV is never good, even if we're
      storing it as a tempfile!
      (Done!)

TODO: Let playlist filter match things lowercase. '72 Minutes Of Fame' should
      be matched if '72 Minutes of Fame' can't be! (However, it would also be
      best to prioritize a case-sensitive match before a non-case-sensitive
      one. Given the input 'FoObAR', prioritize 'FoObAR' over 'Foobar'.)
      (Done!)

TODO: Figure out why written track files (when using HTTP downloader) are
      URL-encoded. It's probably writing a file based on the href-file name,
      rather than the title. That's alright, but maybe we should URL-decode
      and then sanitize the href-file name, so that we get 'Foo Bar.mp3'
      instead of 'Foo%20Bar.mp3'.
      (Done!)

TODO: Make max download attempts variable by the user (without requiring
      source editing, obviously).
      (Done!)

TODO: Update HTTP crawl man page to include new options, and maybe update
      the HTTP crawler itself to reveal more options to the command line.

TODO: Fix the bug in loop-play.js where wasDestroyed doesn't exist!
      (Done!)

TODO: Use `mpv` instead of `play`!!!!!!!!! This would fix every problem ever.

TODO: It looks like up-next doesn't seem to work properly when using the
      YouTube downloader; though it's possible we'll be scrapping downloaders
      altogether..