rpm spec file: use standard group

resolve rpmlint warning: non-standard-group System/Libraries
rpm spec file: follow package guidelines for version

resolve rpmlint warning:

    invalid-url Source0: ...  HTTP Error 404: Not Found

Challenges:

* duosecurity/duo_unix does not have git tags
* duosecurity/duo_unix does not appear to routinely
  indicate published version in git log

Therefore:

This patchset attempts to meet the spirit of packaging
guidelines by combining the advice from both:

* http://fedoraproject.org/wiki/Packaging:SourceURL#Github
* http://fedoraproject.org/wiki/Packaging:NamingGuidelines#Snapshot_packages
rpm spec file: use local copy of libtool instead of rpaths

resolve rpmbuild failure on fedora due to fatal error:

    0001: file -snip- contains a standard rpath '/usr/lib64' in [/usr/lib64]
rpm spec file: provide correct paths for doc files

resolve rpmbuild failure due to non-standard doc file location
rpm spec file: tag man pages as docs
rpm spec file: add changelog entries
rpm spec file: comment-out packager

resolve rpmlint warning:

    The Packager tag is hardcoded in your spec file.
    It should be removed, so as to use rebuilder's own defaults.