Log Message:
p5-Spreadsheet-Read: update to 0.79.

0.79	- 29 Aug 2018, H.Merijn Brand
    * Environmant control hardening
    * ReadData () docs (opening from scalar ref: issue#21)
    * Check for XLSX content on opening from plain scalar content
    * Fix typo in ss-dup-tk.pl (PRC, Branislav Zahradnik)
    * Allow source from command line option in xls2csv (PRC, Branislav Zahradnik)
    * Allow --in-sep=tab in xlscat/xlsgrep
    * Add --hash to xlscat/xlsgrep
    * Help and usage for examples/xls2csv PR#23)