Drop libidn

Instead, we use the pure Ruby IDNA solution in addressable.

Close #66.

README.md

@@ -157,10 +157,7 @@ url.normalized.to_s           # => "https://admin:correcthorsebatterystaple@www.
 
 ### Dependencies
 
-The gem requires libidn.
-
-    sudo apt-get install libidn11 # Ubuntu
-    brew install libidn # OS X
+Only the gems listed in the [Gem Specification](https://github.com/twingly/twingly-url/blob/master/twingly-url.gemspec).
 
 ## Development
 

lib/twingly/url.rb

@@ -1,5 +1,4 @@
 require "addressable/uri"
-require "addressable/idna/native"
 require "public_suffix"
 
 require_relative "public_suffix_list"
@@ -17,7 +16,6 @@ class URL
     ERRORS_TO_EXTEND = [
       Addressable::URI::InvalidURIError,
       PublicSuffix::DomainInvalid,
-      IDN::Idna::IdnaError,
     ]
 
     private_constant :ACCEPTED_SCHEMES

spec/lib/twingly/url_spec.rb

@@ -42,9 +42,6 @@ def invalid_urls
     # https://github.com/sporkmonger/addressable/issues/224
     "http://some_site.net%C2",
     "http://+%D5d.some_site.net",
-
-    # Triggers IDN::Idna::IdnaError: Output would be too large or too small (5)
-    "http://AcinusFallumTrompetumNullunCreditumVisumEstAtCuadLongumEtCefallumEst.com",
   ]
 end
 
@@ -63,6 +60,21 @@ def valid_urls
     "http://:@blog.twingly.com/",
     "https://www.foo.ایران.ir/bar",
     "https://www.foo.xn--mgba3a4f16a.ir/bar",
+
+    # The following URL triggers
+    #
+    #   IDN::Idna::IdnaError: Output would be too large or too small (5)
+    #
+    # when used with Addressable and libidn (IDNA 2003)
+    # but considered valid with the pure Ruby IDNA solution in Addressable.
+    #
+    # This inconsistency has as been reported at
+    # https://github.com/sporkmonger/addressable/issues/239
+    #
+    # Long names like this will probably not resolv, see comments at
+    # https://github.com/twingly/twingly-url/issues/66#issuecomment-246349029
+    # but for now as addressable considers them valid, we do the same.
+    "http://AcinusFallumTrompetumNullunCreditumVisumEstAtCuadLongumEtCefallumEst.com",
   ]
 end
 

twingly-url.gemspec

@@ -14,7 +14,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency "addressable", "~> 2.4", ">= 2.4.0"
   s.add_dependency "public_suffix", "~> 2.0", ">= 2.0.2"
-  s.add_dependency "idn-ruby", "~> 0.1"
 
   s.add_development_dependency "rake", "~> 10"
   s.add_development_dependency "rspec", "~> 3"