Add proxy option

[paratskyi]

After bumping valvat from 1.1.5 to 1.4.0, we cannot set a proxy for the Net::HTTP request. My suggestion is to add proxy option to http option to set proxy for the http client.

Fixed with patch and options

{ open_timeout: 10, read_timeout: 10, proxy: { p_addr: 'proxy_address', p_port: 'proxy_port'} }

class Valvat
  class Lookup
    class Base
      private

      def send_request(uri)
        proxy_options = @options[:http].delete(:proxy)

        if proxy_options
          proxy_args = proxy_options.values_at(:p_addr, :p_port, :p_user, :p_pass).compact
          request = build_request(uri)
          Net::HTTP.start(uri.host, uri.port, *proxy_args, options_for(uri)) do |http|
            http.request(request)
          end
        else
          super
        end
      end
    end
  end
end