Create the allow_values matcher

It is a alias to the actual allow_value matcher.

NEWS.md

@@ -77,6 +77,13 @@
 
 * Add `join_table` qualifier to `have_and_belong_to_many`. ([#556])
 
+* `allow_values` is now an alias for `allow_value`. This makes more sense when
+  checking against multiple values:
+
+    it { should allow_values('this', 'and', 'that') }
+
+  ([#692])
+
 [#402]: https://github.com/thoughtbot/shoulda-matchers/pull/402
 [#587]: https://github.com/thoughtbot/shoulda-matchers/pull/587
 [#662]: https://github.com/thoughtbot/shoulda-matchers/pull/662
@@ -94,6 +101,7 @@
 [#556]: https://github.com/thoughtbot/shoulda-matchers/pull/556
 [#457]: https://github.com/thoughtbot/shoulda-matchers/pull/457
 [#694]: https://github.com/thoughtbot/shoulda-matchers/pull/694
+[#692]: https://github.com/thoughtbot/shoulda-matchers/pull/692
 
 # 2.8.0
 

lib/shoulda/matchers/active_model/allow_value_matcher.rb

@@ -194,6 +194,7 @@ module Shoulda
           AllowValueMatcher.new(*values)
         end
       end
+      alias_method :allow_values, :allow_value
 
       # @private
       class AllowValueMatcher

spec/unit/shoulda/matchers/active_model/allow_value_matcher_spec.rb

@@ -1,5 +1,13 @@
 require 'unit_spec_helper'
 
+describe Shoulda::Matchers::ActiveModel do
+  describe '#allow_values' do
+    it 'is aliased to #allow_value' do
+      expect(method(:allow_values)).to eq(method(:allow_value))
+    end
+  end
+end
+
 describe Shoulda::Matchers::ActiveModel::AllowValueMatcher, type: :model do
   context "#description" do
     it 'describes itself with multiple values' do