title: How to create an in-memory object that can be used as a Reader, Writer, or Seek in Rust?
body: <p>I need a completely in-memory object that I can give to <code>BufReader</code> and <code>BufWriter</code>. Something like Python's <code>StringIO</code>. I want to write to and read from such an object using methods ordinarily used with <code>File</code>s.</p>
  
  <p>Is there a way to do this using the standard library?</p>