Ring middleware for common response headers

 ring-headers is a Ring middleware collection for adding and manipulating
 common response headers. It provides middleware for:
 .
  * replacing relative redirects with absolute redirects. Useful
    for clients that do not yet implement RFC 7231.
  * automatically adding a charset to the content-type header in
    response maps.
  * handling headers set by HTTP proxies.
  * adding various 'X-' response headers.