reports success when 301

[christophermlne]

https://github.com/tedconf/ember-cli-deploy-front-end-builds/blob/master/lib/front-end-builds-notifier.js#L83

We recently ran into a problem deploying to our staging environment. I was using http instead of https for the endpoint and notification was rejected with a 301.

This user feedback in the terminal was a success message instead of an error.