code: public static Observable<String> decode(Observable<byte[]> src, String charsetName) {
          return decode(src, Charset.forName(charsetName));
      }
docs: Decodes a stream of multibyte chunks into a stream of strings that works on infinite streams
  and where handles when a multibyte character spans two chunks.
  <p>
  <img width="640" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/St.decode.png" alt="">
  
  @param src
  @param charsetName
  @return the Observable returning a stream of decoded strings