Implement 'replay' command

[nc6]

Replay command should replay everything in a session. Optionally, it should then drop you into a terminal after having replayed. More options should include:

• Only replaying successful commands
• Only replaying commands from the last n days, for example.
• Verifying that the output of commands was the same as last time (tricky, since we don't have exact times on individual characters for stdin, for example).

[nc6]

Also the difference between replaying just commands and replaying all of stdin.