Add Yahoo! Answers plugin

The .answer command will search Yahoo! Answers with the given query and
respond with one of the 'chosen' answers returned by Yahoo's API and a
link to the question.

plugins/yahooanswers.py

@@ -0,0 +1,31 @@
+from util import hook, http
+from random import choice
+
+@hook.command
+def answer(inp, bot=None):
+    ".answer <query> -- find the answer to a question on Yahoo! Answers"
+
+    url = "http://answers.yahooapis.com/AnswersService/V1/questionSearch"
+    app_id = bot.config.get("api_keys", {}).get("yahoo", None)
+
+    if app_id is None:
+        return "error: yahoo appid not set"
+
+    result = http.get_json(url,
+                query=inp,
+                search_in="question",
+                output="json",
+                appid=app_id)
+
+    questions = result.get("all", {}).get("questions", [])
+    answered = filter(lambda x: x.get("ChosenAnswer", ""), questions)
+
+    if not answered:
+        return "no results"
+
+    chosen = choice(answered)
+    answer, link = chosen["ChosenAnswer"], chosen["Link"]
+    response = "%s -- %s" % (link, answer)
+
+    return " ".join(response.split())
+