From switch to if/elsif/else in Server::SSL

Per @tarcieri comment at https://github.com/celluloid/reel/pull/121#discussion-diff-8277201R29

ssl_context.verify_mode =
  case
  when options.include?(:verify_mode) then options[:verify_mode]
  when options.include?(:ca_file)     then OpenSSL::SSL::VERIFY_PEER
  when options.include?(:ca_path)     then OpenSSL::SSL::VERIFY_PEER
  else                                     OpenSSL::SSL::VERIFY_NONE
  end

The above ought to be more idiomatic, and done with if/elsif/else approach.

@stouset, can you refactor that? I believe that came as part of your recent upgrades to what is now Server::SSL?

celluloid / reel

From switch to if/elsif/else in Server::SSL #124