Automatic HEAD handling

[cyco130]

We should provide a middleware for automatically handling HEAD requests by stripping the body from GET responses.

We can provide two flavors, one that always handles and one that handles only unhandled ones.

[aleclarson]

Just a note: I think this would need to be done at the router level, so you can differentiate between a GET handler and a HEAD handler. With the latter, you wouldn't want to interfere.

[cyco130]

I agree, it belongs to the router.