Config must request to writeJsonFile otherwise will not

Found that karma-coverage is creating a json file every run. I don't need it and would like to avoid writing a grunt task to delete these extra files. I'd like to see it disabled by default.

With this change, if you need the json, then include this in your karma.conf
        coverageReporter: {
             writeFile: true
        }

Open to different ways to do this, just give me some feedback and I'll get it done.