YouTube API is old

YouTube API is old. So the source code which is related to YouTube API doesn't work (youtube.py and youtube2.py).
- intro/youtube2.py

```
import requests
url = "https://gdata.youtube.com/feeds/api/standardfeeds/top_rated?alt=json"
response = requests.get(url)
data = response.json()
for video in data['feed']['entry'][0:6]:
    print(video['title']['$t'])
```
