message: Add error silencing to the readme example
diff: @@ -39,6 +39,9 @@ fn main() -> hdf5::Result<()> {
  use self::Color::*;
  use ndarray::{arr1, arr2};
  + // so that libhdf5 doesn't print errors to stdout
  + let _ = hdf5::silence_errors();
  +
  {
  // write
  let file = hdf5::File::open("pixels.h5", "w")?;
  