Fixed undefined destination filename, inc constellation with grunt-newer and grunt-contrib-watch

With grunt build everything worked fine. But when I used grunt watch I get the error "Warning: Unable to write "undefined" file (Error code: undefined). Use --force to continue."
Because this.data.dest was not defined in this context. this.data.files alias this.files has the right destination filename. Inspired by grunt-contrib-coffee I wrote this bugfix and it "grunt watch" worked now correctly.