Set up New Relic on snapshot server [#80760092]

https://www.pivotaltracker.com/story/show/80760092

Add new relic configuration file for the staging server.

Require new relic  :)

Pluck NewRelic key from the environment.

ignore newagent log files.

Pluck NewRelic app_name from the environment.

Explicitly add rack instrumentation.  NB:  Don't know if we need this particularly.