Supported "Recipe Category Ranking" call without "category_id"

[kakakakakku]

What is this

Hi !
I found that "Recipe Category Ranking" should call without category_id like this.

$ curl -s https://app.rakuten.co.jp/services/api/Recipe/CategoryRanking/20121121?applicationId=123 | jq .result[].recipeTitle
$ curl -s https://app.rakuten.co.jp/services/api/Recipe/CategoryRanking/20121121?applicationId=123&categoryId=15 | jq .result[].recipeTitle
$ curl -s https://app.rakuten.co.jp/services/api/Recipe/CategoryRanking/20121121?applicationId=123&categoryId=10-276 | jq .result[].recipeTitle

省略時の場合は総合ランキング
https://webservice.rakuten.co.jp/api/recipecategoryranking/

So, I supported that can call method without category_id like this.

> items = RakutenWebService::Recipe.ranking
> items = RakutenWebService::Recipe.ranking('15')
> items = RakutenWebService::Recipe.ranking('10-276')

Please review, thanks !

[satoryu]

@kakakakakku thank you for opening your pull-reqeust 👍 this PR will be shipped with the next version.