Set up configuration for Python app monitoring

This is a bare-bones setup, as generated by `newrelic-admin generate-config <license_key> newrelic.ini`.

In order to use this, we'll have to plop `newrelic.ini` somehwere and change our command in supervisor to launch with newrelic.

Our old run is simply:

```
command=/usr/share/nbviewer/venv/bin/python -m nbviewer --port=8080 --processes=8 --mc_threads=4
```

We'll now switch to 
```
command=/usr/share/nbviewer/venv/bin/newrelic-admin run-python -m nbviewer --port=8080 --processes=8 --mc_threads=4
```

newrelic was already part of the old requirements file, so we're good to go in the virtualenv.