Add OxfordDictionary::Client#entry_snake_case

For V2 we are going to stop snake casing the keys of the response. If
someone needs more time to upgrade their code, they can transition for
this call (which will continue to return the snake cased keys).

I plan on removing this in the next major version upgrade.

lib/oxford_dictionary/client.rb

@@ -40,6 +40,12 @@ def entry(*args)
       end
     end
 
+    def entry_snake_case(word:, dataset_name: 'en-gb', params: {})
+      warn 'Client#entry_snake_case is DEPRECATED. Use Client#entry instead.'
+      entry_endpoint.
+        entry_snake_case(word: word, dataset_name: dataset_name, params: params)
+    end
+
     private
 
     def entry_endpoint

spec/client_spec.rb

@@ -37,4 +37,19 @@
       end
     end
   end
+
+  describe '#entry_snake_case' do
+    let(:client) { described_class.new(app_id: app_id, app_key: app_key) }
+    subject { client.entry_snake_case(word: word, params: params) }
+
+    let(:word) { 'ace' }
+    let(:params) { {} }
+
+    it 'calls Entries#entry_snake_case' do
+      expect_any_instance_of(OxfordDictionary::Endpoints::Entries).
+        to receive(:entry_snake_case).
+        with(word: word, dataset_name: 'en-gb', params: params)
+      subject
+    end
+  end
 end