This still doesn't correctly handle the shorter "effective lengths" for handles
and URLs. And it doesn't handle different per-server toot lengths. But it does
catch posts that become too long because the length of the CW is counted as part
of the length of the post body, and gives a validation error rather than
throwing an exception.
Only supports single user, lots of display elements not supported yet.
But it actually has something to show.
Actually display a home timeline.
Still only single user, doesn't correctly handle boosts, CWs, and
probably a lot of other things.
