t.retweet_date should represents when retweeted (#563)

* t.retweet_date should represents when retweeted

* should cast to int before bit shift

twint/tweet.py

@@ -98,7 +98,7 @@ def Tweet(tw, config):
     t.user_rt_id, t.user_rt = getRetweet(tw)
     t.retweet = True if t.user_rt else False
     t.retweet_id = tw['data-retweet-id'] if t.user_rt else ''
-    t.retweet_date = datetime.fromtimestamp(((t.id >> 22) + 1288834974657)/1000.0).strftime("%Y-%m-%d %H:%M:%S") if t.user_rt else ''
+    t.retweet_date = datetime.fromtimestamp(((int(t.retweet_id) >> 22) + 1288834974657)/1000.0).strftime("%Y-%m-%d %H:%M:%S") if t.user_rt else ''
     t.quote_url = getQuoteURL(tw)
     t.near = config.Near if config.Near else ""
     t.geo = config.Geo if config.Geo else ""