There was some doubt on gitter about sleuth generating spans with floating-point
rendered timestamps. While this shouldn't break people we certainly shouldn't
create json like this.
This was presumed to be caused by sleuth's rest template sender by @mojsha who
was trying Jaeger. Jaeger's parser doesn't give any errors with a 400.
```json
[
{
"traceId": "a65dac9d8bbb57f8",
"parentId": "a65dac9d8bbb57f8",
"id": "f223bb97e1eba9b2",
"kind": "SERVER",
"name": "https:\/hello3",
"timestamp": 1.521027116604e+15,
"duration": 1525,
"localEndpoint": {
"serviceName": "${spring.application.name}",
"ipv4": "10.128.6.98",
"port": 8443
},
```
I added a test to make sure it is not the case.
eb34bfbedb