fix rspec warning

spec/models/article_spec.rb

@@ -103,7 +103,7 @@ describe Article do
       article.update_attributes! updated_article.attributes.reject{|k,v| k=='id' or k=='type'}
       expect(article.unit).to eq '200g'
       expect(article.unit_quantity).to eq 5
-      expect(article.price).to be_close(shared_article.price/5, 1e-3)
+      expect(article.price).to be_within(1e-3).of(shared_article.price/5)
     end
   end
 end