[skip travis] create faq.md

how to redirect to another extractor

docs/faq.md

@@ -0,0 +1,31 @@
+- Q: How to redirect to another extractor?  
+  - A:
+    - Most simple using only `url_result` 
+      ```
+      # get proper url first if needed.
+      return self.url_result(url)
+      ```
+    - Using `_request_webpage` and `to_screen` in addition
+      ```
+      urlh = self._request_webpage(
+          url, id, note='Downloading redirect page')
+      url = urlh.geturl()
+      self.to_screen('Following redirect: %s' % url)
+      return self.url_result(url)
+      ```
+    - Using `return` construction
+      ```
+      return {
+            '_type': 'url_transparent',
+            'url': url, 
+            'ie_key': ExampleIE.ie_key(),
+            'id': id,
+        }
+      # Alternative if extractor supports internal uri like kaltura
+      return {
+            '_type': 'url_transparent',
+            'url': 'kaltura:%s:%s' % (partner_id, kaltura_id), 
+            'ie_key': KalturaIE.ie_key(),
+            'id': id,
+        }
+      ```