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:

```
/usr/share/nbviewer/venv/bin/python -m nbviewer --port=8080 --threads=8
```

Since `newrelic-admin` has to be the one invoking the program, we'll also need to `pip install newrelic`.

```
NEW_RELIC_CONFIG_FILE=newrelic.ini /usr/share/nbviewer/venv/bin/newrelic-admin nbviewer --port=8080 --threads=8
```