Use native Ruby implementations in Yast::URL and Yast::IP

@cwh42 I am creating a PR so that I can comment on the code early.
BTW you can look at libzypp URL tests, you can find some nice examples like [this](https://github.com/openSUSE/libzypp/blob/master/tests/zypp/Url_test.cc#L208) or [this](https://github.com/openSUSE/libzypp/blob/master/tests/zypp/Url_test.cc#L228)... :wink: