Broadcast writing on README no longer compiles (due to removal of `broadcast()`)

[tatsuya6502]

The "broadcast writing (simple file copying)" example on the README.md no longer compiles. This is because Writer::broadcast() was never stabilized and removed from Nightly libstd on Mar 8, 2016.

I think a simple workaround is to change the example as the followings:

extern crate pbr;

use std::io::copy;
use pbr::{ProgressBar, Units};
use std::fs::File;
use std::io::Write;

fn main() {
    let mut file = File::open("/usr/share/dict/words").unwrap();
    let n_bytes = file.metadata().unwrap().len() as usize;
    let mut pb = ProgressBar::new(n_bytes as u64);
    pb.set_units(Units::Bytes);
    let mut handle = File::create("copy-words").unwrap();
    {
        let mut tee = TeeWriter::new(&mut handle, &mut pb);
        copy(&mut file, &mut tee).unwrap();
    }
    pb.finish_print("done");
}

/// Tee (T-Split) Writer writes the same data to two child writers.
struct TeeWriter<'a, T1: Write + 'a, T2: Write + 'a> {
    w1: &'a mut T1,
    w2: &'a mut T2,
}

impl<'a, T1, T2> TeeWriter<'a, T1, T2>
where
    T1: Write + 'a,
    T2: Write + 'a,
{
    fn new(w1: &'a mut T1, w2: &'a mut T2) -> Self {
        Self { w1, w2 }
    }
}

impl<'a, T1, T2> Write for TeeWriter<'a, T1, T2>
where
    T1: Write + 'a,
    T2: Write + 'a,
{
    #[inline]
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        let size1 = self.w1.write(buf)?;
        let size2 = self.w2.write(buf)?;
        Ok(size1.min(size2))
    }

    #[inline]
    fn flush(&mut self) -> std::io::Result<()> {
        self.w1.flush()?;
        self.w2.flush()
    }
}

Or, for convenience, maybe we can add something like TeeWriter above to this crate.

I could work on either ideas. Please let me know your thoughts.

[a8m]

Thanks for reporting this issue @tatsuya6502. I'm not sure if having something like TeeWriter should be part of this crate. However, I think we can start with updating the README, and then see what other people have to say about it.