simple fix for bug reported by Tuan-Anh in processing the following e…

…xample tweet:

Early Engagement Consultant - American Express: ( #Madison , WI) http://t.co/zCOAvdsJ #BusinessMgmt #Job #Jobs #TweetMyJobs

python/pos_tag/features.py

@@ -154,7 +154,8 @@ def _check_bigrams(self, word1, word2, use_first):
         bigram = word1 + '_' + word2
         new_features = []
         for dict_name, d in self.bigram_dictionaries.iteritems():
-            if bigram in d.token_pos_set:
+            if bigram != ":_(" and bigram in d.token_pos_set:
+                print bigram
                 tag1, tag2 = d.token_pos_set[bigram].items()[0][0].split('_')
                 tag = (use_first and tag1) or tag2
                 ttype = (use_first and 'AFTER') or 'BEFORE'