s3-fleet v0.2.1

New features:

• known-hosts --cached on a machine that has not read the fleet yet now says how to fill the cache (s3-fleet -f FLEET list), instead of only reporting a missing file.

Documentation:

• Every command's man page now describes the command, not just its name.
• s3-fleet-ssh(1) says which ssh options the wrapper adds, that it replaces itself with ssh, and that once ssh runs the exit status is ssh's (the remote command's, or 255), with a recipe for callers that must tell s3-fleet's codes apart. It also shows that ssh options after the host still apply, with a ControlMaster example.
• s3-fleet-known-hosts(1) says that --cached never reads the network, what happens with no cache, and which commands fill it.