TODO

   1 - [ ] Support redirects
   2   - should permanent redirects update the feed somehow?
   3 - [ ] Support time ranges (i.e. reading the timeline between given time points)
   4 - [ ] Implement rfc3339->epoch and remove dependency on rfc3339-old
   5 - [ ] remove dependency on http-client
   6 - [ ] optional text wrap
   7 - [ ] write
   8 - [x] caching (use cache by default, unless explicitly asked for update)
   9   - [x] value --> cache
  10   - [x] value <-- cache
  11     requires: d command
  12 - [ ] timeline limits
  13 - [ ] feed set operations (perhaps better done externally?)
  14 - [ ] timeline as a result of a query (feed set op + filter expressions)
  15 - [ ] named timelines
  16 - [ ] config files
  17 - [ ] parse "following" from feed
  18   - following = <nick> <uri>
  19 - [ ] parse mentions:
  20   - @<source.nick source.url> | @<source.url>
  21 - [ ] highlight mentions
  22 - [ ] filter on mentions
  23 - [ ] highlight hashtags
  24 - [ ] filter on hashtags
  25 - [ ] hashtags as channels? initial hashtag special?
  26 - [ ] query language
  27 - [ ] console logger colors by level ('error)
  28 - [ ] file logger ('debug)
  29 - [-] commands:
  30   - [x] r | read
  31     - see timeline ops above
  32   - [ ] w | write
  33     - arg or stdin
  34     - nick expand to URI
  35   - [ ] q | query
  36     - see timeline ops above
  37     - see hashtag and channels above
  38   - [x] d | download
  39   - [ ] u | upload
  40     - calls user-configured command to upload user's own feed file to their server
  41   Looks like a better CLI parser than "racket/cmdline": https://docs.racket-lang.org/natural-cli/
  42   But it is no longer necessary now that I've figured out how to chain (command-line ..) calls.
  43 - [ ] Suport immutable timelines
  44     - store individual messages (possibly in something like DBM or SQLite)