Fix #54 - Fetch remote accounts by URL from mentions

Fetching atom extracted from FetchRemoteAccountService and FetchRemoteStatusService
into FetchAtomService. Mentions of the constant "http://activityschema.org/collection/public"
skipped as it's not a real URL/user.

app/services/fan_out_on_write_service.rb

@@ -23,7 +23,7 @@ class FanOutOnWriteService < BaseService
   def deliver_to_mentioned(status)
     status.mentions.each do |mention|
       mentioned_account = mention.account
-      next unless mentioned_account.local?
+      next if !mentioned_account.local? || mentioned_account.id == status.account_id
       FeedManager.instance.push(:mentions, mentioned_account, status)
     end
   end