Add IGNIE

Only for www.ign.com, it doesn't support country specific versions (like es.ign.com)

youtube_dl/extractor/__init__.py

@@ -27,6 +27,7 @@ from .googlesearch import GoogleSearchIE
 from .hotnewhiphop import HotNewHipHopIE
 from .howcast import HowcastIE
 from .hypem import HypemIE
+from .ign import IGNIE
 from .ina import InaIE
 from .infoq import InfoQIE
 from .instagram import InstagramIE