Kapacitor data volume mount

Nobody has claimed this yet.

This issue is related to issue #56.

Data from kapacitor didn’t show up at the volume mounting point on the host.
Below is a part of my docker-compose file:
```yaml
influxdb...
chronograf...

kapacitor:
image: kapacitor:1.5
container_name: kapacitor
hostname: kapacitor
volumes:
# Data directory
- /var/metrics/data/kapacitor:/var/lib/kapacitor
# Configuration
- /var/metrics/config/kapacitor:/etc/kapacitor
environment:
KAPACITOR_INFLUXDB_0_URLS_0: http://influxdb:8086
KAPACITOR_LOGGING_FILE: STDOUT
KAPACITOR_LOGGING_LEVEL: ERROR
links:
- influxdb
depends_on:
- influxdb
```

After investigating inside the docker container to find out where the kapacitor data were stored I found it at `/root/.kapacitor`.
I changed the mapping to this folder and the everything works fine.
```yaml
# Data directory
- /var/metrics/data/kapacitor:/root/.kapacitor
```
Why isn’t the data stored in `/var/lib/kapacitor`?

Looking at the [config](https://github.com/influxdata/influxdata-docker/blob/master/kapacitor/1.5/kapacitor.conf) that’s being copied in the Dockerfile, it looks fine.

Start with kapacitor/1.5/kapacitor.conf and the Dockerfile referenced in the issue, then compare their configured data path with the container path observed at /root/.kapacitor. Reproduce the supplied docker-compose volume mapping and determine which path the image actually uses; document or correct the configuration so the intended host mount contains Kapacitor data.

Written by the indexing model from the issue text.