Segment

We are currently tracking all route changes inside ember. This covers normal page views as well as ember's push-state URL changes. The five events in the story, https://www.pivotaltracker.com/story/show/80575808, are tracked server-side.

Questions:
- move all these analytics calls into one file? This would allow us to write one-liners in the rest of the code.
- any feedback on the event names? `event: 'Paper#updated (submitted=true)',`
- any other data you think we should be recording for any of these tracking calls?

We did not commit this, but we created segment projects for development, staging, and production. Google analytics segment adapters for each of these projects are not set up. Heap analytics segment adapters are set up for development and production but not staging.

— RW + DT
Let's include this only if someone has configured Segment.io. One way is to wrap this in `if ENV.has_key 'SEGMENT_IO_WRITE_KEY'`.