polish the paper

Many encoders are adopted in various texts to transform characters into bytes. Local encoders (ASCII, GB-2312) always encode specific characters into shorter bytes. But only universal encoders (UTF-8, UTF-16) can encode whole Unicode set with more space cost and become more and more having general approval. And some other encoders (SCSU, BOCU-1 and binary encoders) lack of self-synchronizing. 

Duncode devotes to encode whole Unicode characters in high space efficiency as local encoders. Multi characters of a string can be compressed into a Duncode unit with less bytes. Duncode shows a great advantage over UTF8 in space efficiency at the expense of less self-synchronizing identification information.  The application is released at \url{https://github.com/NAME_1/duncode}. 

We also build a benchmark, including 179 languages, for character encoder evaluation on different languages at \url{https://github.com/NAME_1/NAME_2txt}.

