Fixed miomio download of sina video

Thanks for the useful program.  

When I tried to get a sina video from a miomio address, the current version `0.3.30dev-48cdcde` does not work.   Further analysis shows that miomio seems to be returning its own id for a video in sina.com, and its player calls an API: ```http://www.miomio.tv/mioplayer/mioplayerconfigfiles/sina.php?vid=[vid returned by miomio]``` to get the xml which should have been returned by http://v.iask.com previously. 

Hence the following patch, which I found to be working at least for me.