Twitter's API sends tweet data with the 'in_reply_to_screen_name' set for non-replies

Currently, txTwitter's `FakeTweet` relies on a tweet being a reply for `in_reply_to_screen_name` to be set. However, Twitter sets `in_reply_to_screen_name` regardless of whether the tweet was a reply or not, as long as the tweet's content begins with a mention.