special case heroku router

The Heroku router has a log line convention described here: https://devcenter.heroku.com/articles/http-routing#heroku-router-log-format

This feature will read the Host field in the syslog packet looking for the string "router." If a match is had, we will parse the structured data and massage it to match the l2met convention. Furthermore, we will prefix the measurement name with the parsed host field in the log line.

Example:

```
at=info method=POST path=/logs?resolution=1000 host=l2met-vis.herokuapp.com request_id=3f791410bc9610716113a84298e070f8 fwd="50.16.79.127" dyno=web.4 connect=1ms service=2ms status=200 bytes=0
```

Would produce the bucket:

bucket1 = {name="l2met-vis.herokuapp.com.service" vals=[2]}
bucket2 = {name="l2met-vis.herokuapp.com.connect" vals=[1]}
bucket3 = {name="l2met-vis.herokuapp.com.bytes" vals=[0]}