Update README with version information.

Include remarks from discussion with Jay <jeronwunalu@gmail.com>.

Note that POIU 1.31.1 should work with 3.1.7.

The latest test.lisp from this revision should work with that old combination
(e.g. copy it as newtest.lisp).

Use $0 in the shell part so the file can be renamed.

Print errors with format! so no need for finish-output.

NB: Still breaking when using with ASDF 3.3 vs 3.2.

Add support for using Quicklisp. You still must download beforehand.

Use publicly available data files for the test, and make it easy
to configure where the test files are downloaded.

Better document the test file itself.

Adapt POIU to the significantly refactored ASDF 3.3 code base, whereby
the cache was generalized to a multi-phase session, into which was moved
a lot of data formerly in the plan object.

Do away with reify-action except for pretty printing, and there reuse
ASDF's new equivalent action-path function.

because the new syntax-control branch of asdf has context wrapping methods in the former.

The above bug was particular bad, because it would cause asdf
to spuriously be reloaded, which would interfere with poiu itself,
and cancel extensions such as cffi-grovel, etc.

Also, better fix posix-waitpid on allegro.

Also, add a README file.

1.29.14: Make it work with 2.32, factoring an action-effectively-done-p around action-already-done-p

when not forcing. Make it work properly with ASDF 2.26.172.