libreoffice warnings cause convert to fail

[nik0kin]

These errors are sent to stderr, then causing the node-unoconv code to think it failed.

Error: Warning: -headless is deprecated.  Use --headless instead.
Warning: -invisible is deprecated.  Use --invisible instead.
Warning: -nodefault is deprecated.  Use --nodefault instead.
Warning: -nofirststartwizard is deprecated.  Use --nofirststartwizard instead.
Warning: -nologo is deprecated.  Use --nologo instead.
Warning: -norestore is deprecated.  Use --norestore instead.
Warning: -accept=socket,host=localhost,port=2002;urp;StarOffice.ComponentContext is deprecated.  Use --accept=socket,host=localhost,port=2002;urp;StarOffice.ComponentContext instead.

This is somewhat more of a unoconv problem