Adds ability to specify zipkin http path relative to host

[andystanton]

No description provided.

[andystanton]

I closed and reopened to retrigger the Travis build. The original error suggests an unreliable Kafka test, but this change does not touch any of the Kafka code or dependencies. I've raised #82 to investigate this.

[crispywalrus]

LGTM

as you say you haven't touched anything kafka so it's unlikely that your changes affected those tests. I have only seen broken tests when I've actually broken something. So I have some concern.

[codefromthecrypt]

Thanks!