Feature: HEAD request with open?

[svoop]

It's quite a common task to check whether a URI leads to a dead end or not. For a "simple" HEAD request, handling the many edge cases (SSL, proxy etc) with net/http is very cumbersome and this excellent gem implements already most of these, therefore ...

Would you consider adding HEAD requests to open-uri. Possible API:

URI.open?("http://www.ruby-lang.org/")

The HTTP status of the HEAD request should be interpreted as follows:

• Any 5xx status raises an exception: Server error means it's impossible to tell whether the URI is okay.
• Any 4xx status returns false: The URI is not valid.
• Any other status returns true: The URI is valid.