def head(path, initheader = nil)
      request(Head.new(path, initheader))
    end
Gets only the header from +path+ on the connected-to host.
+header+ is a Hash like { 'Accept' => '*/*', ... }.

This method returns a Net::HTTPResponse object.

This method never raises an exception.

response = nil
Net::HTTP.start('some.www.server', 80) {|http|
response = http.head('/index.html')
}
p response['content-type']