(FACT-607) Include facter man pages in the package for OSX.

Without this commit, the facter man page is not included in the package for OSX.

This commit adds the appropriate directives to ext/osx/file_mapping.yaml
to include facter man pages in the package for OSX.
Merge pull request #709 from geoffnichols/RE-830/facter-2/fix_man_page_osx

(FACT-607) Include facter man pages in the package for OSX.