Add lib/POE/Resource/Clock.pm to MANIFEST.

Help wanted: Migrate build/release process to Dist::Zilla, or advise
on same.  It's complicated right now.  Probably too complicated.
Update sample programs.
Move the signal information out of the signal pipe.

The signal pipe included all signal information.  This reduces the
number of signals that can be dispatched in a single event loop
iteration.  It also limits the amount and/or type of information we
can include in the signal.

This change puts the signal information in a plain Perl list and only
uses the signal pipe to wake up the event loop to dispatch the signals
in a safer place.
Update copyright dates.
Replace POE::Pipe::* guts with IO::Pipely.

This change doesn't change the way POE or its tests use POE::Pipe::*.
All tests pass in my development environment, so I expect no obvious
problems using IO::Pipely.
Add t/10_units/05_filters/51_reference_die.t to MANIFEST.
Eliminate an uninitialized value warning in the tests.