Require Ruby 2.2 or later

.travis.yml

@@ -1,10 +1,5 @@
 language: ruby
 rvm:
-  - 1.8.7
-  - ree
-  - 1.9.3
-  - 2.0.0
-  - 2.1.9
   - 2.2.5
   - 2.3.1
   - ruby-head

domain_name.gemspec

@@ -19,16 +19,16 @@ Suffix List.
   gem.licenses      = ["BSD-2-Clause", "BSD-3-Clause", "MPL-2.0"]
 
   gem.files         = `git ls-files`.split($/)
-  gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
-  gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
+  gem.test_files    = gem.files.grep(%r{^test/})
   gem.require_paths = ["lib"]
 
   gem.extra_rdoc_files = [
     "LICENSE.txt",
     "README.md"
   ]
 
-  gem.add_runtime_dependency("unf", ["< 1.0.0", ">= 0.0.5"])
+  gem.required_ruby_version = ">= 2.2"
+
   gem.add_development_dependency("test-unit", "~> 2.5.5")
   gem.add_development_dependency("bundler", [">= 1.2.0"])
   gem.add_development_dependency("rake", [">= 0.9.2.2", *("< 11" if RUBY_VERSION < "1.9")])

lib/domain_name.rb

@@ -8,7 +8,7 @@
 require 'domain_name/version'
 require 'domain_name/punycode'
 require 'domain_name/etld_data'
-require 'unf'
+require 'unicode_normalize/normalize'
 require 'ipaddr'
 
 # Represents a domain name ready for extracting its registered domain
@@ -286,7 +286,7 @@ class << self
     # Normalizes a _domain_ using the Punycode algorithm as necessary.
     # The result will be a downcased, ASCII-only string.
     def normalize(domain)
-      DomainName::Punycode.encode_hostname(domain.chomp(DOT).to_nfc).downcase
+      DomainName::Punycode.encode_hostname(domain.chomp(DOT).unicode_normalize).downcase
     end
   end
 end

test/test_domain_name-punycode.rb

@@ -91,7 +91,7 @@ class TestDomainName < Test::Unit::TestCase
         '-> $1.00 <--']
     ].each { |title, cps, punycode|
       assert_equal punycode, DomainName::Punycode.encode(cps.pack('U*')), title
-      assert_equal cps.pack('U*').to_nfc, DomainName::Punycode.decode(punycode), title
+      assert_equal cps.pack('U*').unicode_normalize, DomainName::Punycode.decode(punycode), title
     }
   end
 end