GA ping should be disabled when offline

[pselle]

Original report: iopipe/iopipe-js#23

Trying to work offline locally (no internet connection ... caltrain), i couldn't hit my functions because Google Analytics dns lookup fails.

I tried setting iopipeNoStats in serverless.yaml but there seems to be a code issue (i ended up just removing iopipe temporary to work).

Easy to reproduce by turning off your Internet connection and run with serverless offline.