t/Timeline.t: fix test where it inputs junks to watch_unacked_counts(). Now 'assumed' and 'callback' args are tested separately.
Main.pm: remove comment outs in watch_unacked_counts(). If invalid 'level' arg is provided, it's just ignored by Timeline#watch_unacked_counts() method.
README.md: add installing Module::Build::Prereqs::FromCPANfile to "try without installation" section, because otherwise "cpanm --installdeps ." would fail.