filter warnings from gpg by default; watch for unencrypted files...

...and make it easy to subclass such that we can pass through unencrypted
files.
initial add: PerlIO::via::GnuPG::Maybe

A variant of PerlIO::via::GnuPG to allow for passing through unencrypted
files.
pod tweaks
add some basic ::Maybe tests to t/basic.t
autoadd
dumb down our comments...
POD/doc tweaks.
add the latest cpanfile