Revamps the Zipkin Architecture overview

[codefromthecrypt]

This rewrites the instrumentation process overview per experience giving presentations and insights captured in #23

This is intentionally completing one section vs rewriting the whole web site. That's to help us progress incrementally.

See also https://speakerdeck.com/adriancole/introduction-to-distributed-tracing-and-zipkin-at-devopsdays-singapore

[codefromthecrypt]

cc @openzipkin/core @mjbryant @shakuzen @nicmunroe

[codefromthecrypt]

@mjbryant thanks for the review