Send events to Honeybadger Insights in batches

With #170, we have support to send events to Honeybadger Insights. We should extend this mechanism to support sending them in batches. The [API](https://docs.honeybadger.io/api/reporting-events/) endpoint supports [NDJSON](https://en.wikipedia.org/wiki/JSON_streaming#Newline-Delimited_JSON) payload.