fatpacked, standalone `recs` command

A pure-Perl, single-file "recs" command that lets you run operations like `recs xform ...` which should work on Perl 5.8.1 and higher without any additional modules other than those in core Perl.

To try it out:

    curl https://raw.githubusercontent.com/tsibley/RecordStream/fatpackable/recs > recs
    chmod +x recs
    ./recs --help

In the process I moved to Dist::Milla (a nice wrapper around Dist::Zilla) for distribution management to make the build and release process simpler, as well as to take advantage of the better dependency tracking provided by a cpanfile + Dist::Zilla.

The commit messages are worth reading for more details.  I wanted to get this pushed up and being looked at first, but I plan on revamping some of the POD documentation too.