def write_file(filename = 'foo', string = nil)
      raise ExportError, 'Nothing to export for #{filename}.' if string.nil? || string == ""
      f = File.new( File.expand_path(File.join(export_path, filename)), 'w+')
      f.puts string
      f.close
    end
def write_file(filename = 'foo', string = nil)
      raise ExportError, 'Nothing to export for #{filename}.' if string.nil? || string == ""
      f = File.new( File.expand_path(File.join(export_path, filename)), 'w+')
      f.puts string
      f.close
    end
Write the string to a file in the export path.