Collapsing getServiceName, getServiceHost and getServicePid back to being just getName, getHost and getPid

This causes overlap but the intent now will be to always create a span on sender and receiver side to avoid the awkward field names and simplify the structure.
Inlining SpanSource, only used in InMemorySpanSinkSource for testing.
Cleanup unused imports.
Expose number of recorded traces in InMemorySpanSinkSource
Record incoming requests under a fresh span with the parent set to incoming spanId.

This simplifies the merging of span metadata and annotations with the ruby tracer gem output.
Fix file naming issue
Merge pull request #5 from yammer/attach_records_span

Attach records span

To simplify integration and merging of output logs with the ruby tracer gem output we've changed to record annotations in child spans of the external span. This means we can capture additional span metadata such as host and pid servicing the request without colliding with span metadata.