update README
correct she-bang: let 'env' find ruby or we get the OS vendor installed version, instead of our chosen RVM version
eliminate 'properties.rb'; change HTML parser to Nokogiri, but only require it when needed at runtime; add commentary; build on Anton's usage; report runtime activities to stdout; return explicit return code
remove 'sicp.opf' input file because it should be generated each time to update the publication date
update the README