Update addressable to 2.6

[jage]

We're limiting to 2.5 currently:

twingly-url/twingly-url.gemspec

Line 17 in c2218e9

s.add_dependency "addressable", "~> 2.5.2"

Did a quick test, but we need to either change our specs or look into why the protocol is updated:

Failures:

  1) Twingly::URL.parse when given valid urls does not ruin the url "hTTP://blog.twingly.com/"
     Failure/Error: expect(described_class.parse(valid_url).to_s).to eq(valid_url)

       expected: "hTTP://blog.twingly.com/"
            got: "http://blog.twingly.com/"

       (compared using ==)
     # ./spec/lib/twingly/url_spec.rb:124:in `block (5 levels) in <top (required)>'

[dentarg]

It is this change upstream: https://github.com/sporkmonger/addressable/pull/281/files

[dentarg]

I think we should just accept that case of scheme isn't preserved (we could write a spec for it).

[jage]

Yeah I think that's reasonable.