Prefer i.redd.it ID over post ID for reddit image host.

methods/reddit.js

@@ -8,7 +8,7 @@ function reddit(post) {
     return Promise.resolve({
         album: null,
         items: [{
-            id: post.id,
+            id: post.host.id || post.id,
             url: post.url,
             title: post.title,
             datetime: post.datetime,