Shortening documentation line length.

The documentation line was too long there. Shortening. Not so sure about the URL though - a URL shortening hash would make less sense.

IPython/lib/display.py

@@ -21,7 +21,8 b' class YouTubeVideo(object):'
     vid = YouTubeVideo("abc", start=30)
     display(vid)
     
-    To calculate seconds from time as hours, minutes, seconds use int(timedelta(hours=1, minutes=46, seconds=40).total_seconds())
+    To calculate seconds from time as hours, minutes, seconds use:
+    start=int(timedelta(hours=1, minutes=46, seconds=40).total_seconds())
 
     Other parameters can be provided as documented at 
     https://developers.google.com/youtube/player_parameters#parameter-subheader