Related to #89 and #71.

Close #85.

"bundle exec rspec spec/lib/twingly/url_spec.rb" went from

    files took 1.72 seconds to load

to

    files took 0.27164 seconds to load

My shell is a bit fancy, and with the old versions I got this:

    $ cat `bundle show public_suffix`/data/list.txt | wc -l
    preexec: command not found: bundle
       11618

Catch valid URLs being normalized to something that's parsed as NullURL.

Currently, this URL isn't valid, but if we drop libidn (which we talked
about), it would be valid, due to the way Addressable 2.4.0 works.
See comment at: #66 (comment)

Adding this URL to the tests so we will notice the change in behaviour,
if/when we drop libidn.

The ACE prefix is always in the beginning, thus we need to check the
beginning of each part.

https://en.wikipedia.org/wiki/Internationalized_domain_name#ToASCII_and_ToUnicode

Set the latest version as the minimum (because that's the one that was
used when developing and testing twingly-url), but allow for usage of
later non-major versions, to be able to update the version of these gems
in projects using twingly-url, without requiring a new twingly-url
release.

http://guides.rubygems.org/patterns/

Didn't touch idn-ruby because there's currently only one version, 0.1.0,
released: https://rubygems.org/gems/idn-ruby/versions

Close #89.

#90 (comment)

This will print userinfo, user and password for all URLs, which it
didn't do before.

* DRY up to urls example
* Print the same example methods for all URLs in the README