fix bug in JSON generation where there is a comma at the end
fix bug in JSON generation where there is a comma at the end

gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed,gengstrand/clojure-news-feed