Middleware to simplify replying to HEAD requests.

A response to a HEAD request should be identical to a GET request, with the
exception that a response to a HEAD request should have an empty body.


added in 1.2

(head-request request)
Turns a HEAD request into a GET.


added in 1.2

(head-response response request)
Returns a nil body if original request was a HEAD.


added in 1.1

(wrap-head handler)
Middleware that turns any HEAD request into a GET, and then sets the response
body to nil.