Update channels.py for new DW channels

Hi. I'm new here.
I just wanted to contribute with 2 channels from DW (deutsche welle), that weren't included yet.
This two, DW and DW North America are mostly in german.
I have doble checked the urls, and they work perfectly on VLC.
Best Regards, Jaime.
Merge pull request #3 from jaimeroldan/patch-1

Update channels.py for new DW channels