Fixed heroku deployment issues with memcache and New Relic

There were a few issues with this part:

* Typo that said `heroky`
* It doesn't appear that you can add multiple addons at once like was in the markdown README
* The Heroku memcache addon was sunset in favor of memcachier
* The New Relic app name must be set to push data to New Relic (although this might have been part of the challenge?)