Launch ZipKin in docker using tmp-proc.

Demos how to use tmp-proc to run ZipKin in docker in a unittest.

tmp-proc-zipkin

tmp-proc-zipkin provides an example of using tmp-proc to launch dockerized Zipkin in integration tests.

It provides an instance of Proc for launching the Zipkin image, and also provides an instance of Conn that simplifies opening connections to the launched Zipkin service from tests that use tmp-proc.