Use Chromium by default
Use Chromium by default

This fixes #269:
https://github.com/google/aiyprojects-raspbian/issues/269

Change-Id: I476300f564ec8a04c58f75159900a04d831c053a

google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian