Avoid issue where `ember init` stalls on fresh system

There is an issue where (on a fresh system, which has never run bower before), the bower 'opt-in analytics prompt' will show for a sliver of time (since npm refreshes the cli output with a spinning pipe (`\ | / -`). This causes the initial `ember init` to stall indefinitely.

This patch opts out of analytics via .bowerrc, to circumvent the above issue.

More on bower analytics opt-in:
https://github.com/bower/bower/issues/1162