Fix URL in README (#2347)
Fix URL in README (#2347)

Existing URL returns a 404.
Use URL https://zipkin.io/pages/tracers_instrumentation
adriancole/zipkin,adriancole/zipkin,openzipkin/zipkin,twitter/zipkin,adriancole/zipkin,adriancole/zipkin,openzipkin/zipkin,openzipkin/zipkin,openzipkin/zipkin,twitter/zipkin,twitter/zipkin,twitter/zipkin,openzipkin/zipkin