(Fix previous submissions by using the gem file from rubygems.org)

- 0.18.0.beta1
API:
* D-Bus structs have been passed as Ruby arrays. Now these arrays
are frozen.
* Ruby structs can be used as D-Bus structs.
Bug fixes:
* Returning the value for o.fd.DBus.Properties.Get, use the
specific property signature, not the generic Variant
(gh#mvidner/ruby-dbus#97).
- 0.17.0
API:
* Export properties with `dbus_attr_accessor`, `dbus_reader` etc.
(gh#mvidner/ruby-dbus#86).
Bug fixes:
* Depend on rexml which is separate since Ruby 3.0
(gh#mvidner/ruby-dbus#87, by Toshiaki Asai).
Nokogiri is faster but bigger so it remains optional.
* Fix connection in case ~/.dbus-keyrings has multiple cookies, showing
as "Oops: undefined method `zero?' for nil:NilClass".
* Add the missing name to the root introspection node.