message: Report default values in command line help
diff: @@ -1070,31 +1070,31 @@ impl<M: Measurement> Criterion<M> {
  .arg(Arg::with_name("sample-size")
  .long("sample-size")
  .takes_value(true)
  - .help("Changes the default size of the sample for this run."))
  + .help(&format!("Changes the default size of the sample for this run. [default: {}]", self.config.sample_size)))
  .arg(Arg::with_name("warm-up-time")
  .long("warm-up-time")
  .takes_value(true)
  - .help("Changes the default warm up time for this run."))
  + .help(&format!("Changes the default warm up time for this run. [default: {}]", self.config.warm_up_time.as_secs())))
  .arg(Arg::with_name("measurement-time")
  .long("measurement-time")
  .takes_value(true)
  - .help("Changes the default measurement time for this run."))
  + .help(&format!("Changes the default measurement time for this run. [default: {}]", self.config.measurement_time.as_secs())))
  .arg(Arg::with_name("nresamples")
  .long("nresamples")
  .takes_value(true)
  - .help("Changes the default number of resamples for this run."))
  + .help(&format!("Changes the default number of resamples for this run. [default: {}]", self.config.nresamples)))
  .arg(Arg::with_name("noise-threshold")
  .long("noise-threshold")
  .takes_value(true)
  - .help("Changes the default noise threshold for this run."))
  + .help(&format!("Changes the default noise threshold for this run. [default: {}]", self.config.noise_threshold)))
  .arg(Arg::with_name("confidence-level")
  .long("confidence-level")
  .takes_value(true)
  - .help("Changes the default confidence level for this run."))
  + .help(&format!("Changes the default confidence level for this run. [default: {}]", self.config.confidence_level)))
  .arg(Arg::with_name("significance-level")
  .long("significance-level")
  .takes_value(true)
  - .help("Changes the default significance level for this run."))
  + .help(&format!("Changes the default significance level for this run. [default: {}]", self.config.significance_level)))
  .arg(Arg::with_name("test")
  .hidden(true)
  .long("test")
  