Updated gwtgaechannel.md with new project site

gwtgaechannel code moved out of labs folder at dprotti/todomvc repo, since gwtgaechannel won't be accepted in TodoMVC. Perhaps it will be integrated into TasteLang. Meanwhile it will live on its own repo `dprotti/todomvc-gwtgaechannel`.

Additionally this move simplifies continuous integration and generation of annotated sources.