markov: be smarter with appending punctuation

don't append commas ever (it looks weird), ignore other situations
where the chain already ends with punctation so we don't need more

dr_botzo/markov/lib.py

@@ -25,8 +25,8 @@ def generate_line(context, topics=None, min_words=15, max_words=30, max_sentence
         if len(line) >= min_words:
             return line
         else:
-            if line[-1][-1] not in [',', '.', '!']:
-                line[-1] += random.choice([',', '.', '!'])
+            if line[-1][-1] not in [',', '.', '!', '?', ':']:
+                line[-1] += random.choice(['?', '.', '!'])
 
         tries += 1