Fix injection of unicode

As previously discussed, this fixes the injection of unicode when we're already receiving strings in other places.  (If I turn off websockets in my browser, everything stops breaking.)

This fixes one of the two issues we encounter with txircd.

I assume we can receive any JSON over the socket, but the code after the change seems to imply that it's strictly lists.  If we'll really only ever receive lists, let me know and I can simplify this patch a bit.