Tweaks:
* --headers command line option, which can be used to
enable/disable the automatic headers, and the
automatic empty lines between samples.
* --show-timestamps, which changes the #ts line with
a timestamp in the HH:MM:SS format.
* Always use ReadKeyMini, even when we have Term::ReadKey.
In the latter case, use the Term::ReadKey functions,
but if they fail, try again with our own versions.
Fix:
Looks like I forgot to actually enable the "save the current, first
and last" samples. This is now on. It should mean faster and better
output when changing --group-by modes.
b0f7bc4fc6