message: When gnuplot --version errors, don't panic when parsing an empty stdout
diff: @@ -952,8 +952,13 @@ impl Plot {
  /// Returns `gnuplot` version
  // FIXME Parsing may fail
  pub fn version() -> io::Result<(usize, usize, usize)> {
  - let stdout = try!(Command::new("gnuplot").arg("--version").output()).stdout;
  - let mut words = str::from_utf8(&stdout).unwrap().split_whitespace().skip(1);
  + let command_output = try!(Command::new("gnuplot").arg("--version").output());
  + if !command_output.status.success() {
  + let error = str::from_utf8(&command_output.stderr).unwrap();
  + eprintln!("`gnuplot --version` returned an error\n{}", error);
  + return Err(io::Error::new(io::ErrorKind::Other, error));
  + }
  + let mut words = str::from_utf8(&command_output.stdout).unwrap().split_whitespace().skip(1);
  let mut version = words.next().unwrap().split('.');
  let major = version.next().unwrap().parse().unwrap();
  let minor = version.next().unwrap().parse().unwrap();
  