fix issue #3 (missing results for empty lines)

CMUTweetTagger.py

@@ -56,6 +56,7 @@ def _call_runtagger(tweets, run_tagger_cmd=RUN_TAGGER_CMD):
     # 'Listening on stdin for input.  (-h for help)\nDetected text input format\nTokenized and tagged 1 tweets (2 tokens) in 7.5 seconds: 0.1 tweets/sec, 0.3 tokens/sec\n')
 
     pos_result = result[0].strip('\n\n')  # get first line, remove final double carriage return
+    pos_result = pos_result.replace("\n\n","\n\n\n") # avoid missing result for empty lines
     pos_result = pos_result.split('\n\n')  # split messages by double carriage returns
     pos_results = [pr.split('\n') for pr in pos_result]  # split parts of message by each carriage return
     return pos_results