Added Khan Academy support (videos downloaded from YouTube)

src/you_get/downloader/__init__.py

@@ -39,5 +39,6 @@ from .yinyuetai import *
 from .youku import *
 from .youtube import *
 from .ted import *
+from .khan import *
 
 from .__main__ import *

src/you_get/downloader/__main__.py

@@ -60,6 +60,7 @@ def url_to_module(url):
         'youtu': youtube,
         'youtube': youtube,
         'ted': ted,
+        'khanacademy': khan,
         #TODO
     }
     if k in downloads:

src/you_get/downloader/khan.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+
+__all__ = ['khan_download']
+
+from ..common import *
+from .youtube import youtube_download_by_id
+
+def khan_download(url, output_dir = '.', merge = True, info_only = False):
+    page = get_html(url)
+    id = page[page.find('src="https://www.youtube.com/embed/') + len('src="https://www.youtube.com/embed/') :page.find('?enablejsapi=1&wmode=transparent&modestbranding=1&rel=0&fs=1&showinfo=0')]
+    youtube_download_by_id(id)
+
+site_info = "khanacademy.org"
+download = khan_download
+download_playlist = playlist_not_supported('khan')