Fix crash onn storing items with too precise dates

lib/frenzy/update_feeds.ex

@@ -135,7 +135,7 @@ defmodule Frenzy.UpdateFeeds do
       guid: entry.guid,
       title: entry.title,
       url: url,
-      date: entry.date |> Timex.Timezone.convert(:utc),
+      date: entry.date |> Timex.Timezone.convert(:utc) |> DateTime.truncate(:second),
       creator: "",
       content: entry.content
     }