twitter: don't re-encode replyee name

this appears to have been whan was causing replying via twitter to fail.
let's test something while we're here:

fixes #2

dr_botzo/twitter/ircplugin.py

@@ -166,7 +166,7 @@ class Twitter(Plugin):
             return self.bot.reply(event, "you do not have permission to send tweets.")
 
         replyee_tweet = self.twit.show_status(id=status_id)
-        target = replyee_tweet['user']['screen_name'].encode('utf-8', 'ignore')
+        target = replyee_tweet['user']['screen_name']
 
         try:
             reptweet = "@{0:s}: {1:s}".format(target, tweet)