Add an extractor for NBC news (closes #1320)

youtube_dl/extractor/__init__.py

@@ -54,6 +54,7 @@ from .muzu import MuzuTVIE
 from .myspass import MySpassIE
 from .myvideo import MyVideoIE
 from .nba import NBAIE
+from .nbc import NBCNewsIE
 from .ooyala import OoyalaIE
 from .pbs import PBSIE
 from .photobucket import PhotobucketIE