message: Typo in reader.rs
  `not unable` should be just `unable`.
  The sentence otherwise reads as if the current format remains unchanged when a format is guessed.
  The inverse is then also true when no format is guessed the current format is updated, but no value to update it to is guessed.
diff: @@ -138,7 +138,7 @@ impl<R: BufRead + Seek> Reader<R> {
  /// Make a format guess based on the content, replacing it on success.
  ///
  /// Returns `Ok` with the guess if no io error occurs. Additionally, replaces the current
  - /// format if the guess was successful. If the guess was not unable to determine a format then
  + /// format if the guess was successful. If the guess was unable to determine a format then
  /// the current format of the reader is unchanged.
  ///
  /// Returns an error if the underlying reader fails. The format is unchanged. The error is a
  