title: How to build WriteBuf from array
body: <p>I am serializing two values in to an array and I am trying to go through a WriteBuf but I am getting the error that</p>
  
  <pre><code>error: the trait `std::io::Write` is not implemented for the type `[_; 12]`
  error: type `std::io::buffered::BufWriter&lt;&amp;mut [_; 12]&gt;` does not implement any method in scope named `write_be_u32`
  error: type `std::io::buffered::BufWriter&lt;&amp;mut [_; 12]&gt;` does not implement any method in scope named `write_be_f64`
  </code></pre>
  
  <p>Here is the minimum code to generate this error:</p>
  
  <pre><code>use std::io::{ BufWriter, Write };
  
  fn main(){
    let packed_data = [0; 12];
    let timestamp : u32 = 100;
    let value : f64 = 9.9;
  
    let writer = BufWriter::new(&amp;mut packed_data);
    writer.write_be_u32(timestamp);
    writer.write_be_f64(value);
  
    println!("Packed data looks like {:?}", packed_data);
  }
  </code></pre>
  
  <p>Am I no borrowing the slice correctly? Am I note using the proper module to define the <code>Write</code> trait for my buffer?</p>
  
  <p>Here is a playpen for this code: <a href="http://is.gd/ol8qND" rel="nofollow">http://is.gd/ol8qND</a></p>