def open_text filename, extension=nil, options={}
      extension = file_extension(filename) unless extension
      t = text_to_utf8(open(filename).read)
      send("load_#{extension}".to_sym, t, options)
    end
def open_text filename, extension=nil, options={}
      extension = file_extension(filename) unless extension
      t = text_to_utf8(open(filename).read)
      send("load_#{extension}".to_sym, t, options)
    end
Open the file in non-binary, read-only mode, read it and parse it to UTF-8

 @param [String] filename   a string with a reference to the file to be opened
 @param [String] extension  an optional string enforcing a certain parser (based on the file extension, e.g. 'txt', 'csv' or 'xls')