local dev mode that disables service workers

Local development would be much easier if we could disable service workers when developing locally. 
 
We need to investigate options.

It could either not register the service worker or I wonder if we could get away with registering an empty service worker with something like:


``` 
   "service-worker-disabled": "browserify ./client/EMPTYFILE.js > ./docs/service-worker.js"
```
