Uses latest zipkin library in support of simplified json format

[codefromthecrypt]

This uses internal classes to perform a lot of the translation formerly
done here. By updating to latest zipkin, this also allows use of the new
POST /api/v2/spans endpoint from openzipkin/zipkin#1499

I'm happy to support this including work to switch over to the public
zipkin2 types once they become available later this year. In the mean
time, this uses shade to ensure internal types aren't leaked.

[mtwo]

Thanks Adrian!
@bogdandrutu FYI

[codefromthecrypt]

I tested by running the thing like so..

$ GOOGLE_APPLICATION_CREDENTIALS=~/Downloads/zipkin-demo-81ff9558b5aa.json PROJECT_ID=zipkin-demo java -jar ./collector/target/collector*.jar

then I posted data to the new zipkin endpoint:

# make epoch seconds epoch microseconds, because.. microservices!
$ date +%s123456
1502677917123456
$ curl -s localhost:9411/api/v2/spans -H'Content-Type: application/json' -d'[{
  "traceId": "86154a4ba6e91387",
  "id": "86154a4ba6e91387",
  "kind": "SERVER",
  "name": "get",
  "timestamp": 1502677917123456,
  "duration": 207000,
  "localEndpoint": {
    "serviceName": "testservice",
    "ipv4": "113.210.108.10"
  },
  "tags": {
    "http.path": "/api/blah"
  }
}]'

Then, after a few minutes it arrived here: https://console.cloud.google.com/traces/traces?project=zipkin-demo

[codefromthecrypt]

ps here's an openapi spec that does what I did in curl openzipkin/zipkin-api#33

[codefromthecrypt]

mind doing a release of v0.3 so that folks can use this?