Updated recordkeeper.recordThatTopicWasUsedInTribute and topicWasUsedInTribute to normalize to lowercase.
Updated record/topicWasUsedInTribute to save and search using singular forms.
Updated tweetRepliesToStatuses to drop restriction on replying to replies to self but added filter on noun groups to also eliminate topics used in tributes (in addition to existing filter for topics already used to reply to user).