Added alias method chains around sweatshop enqueue, do_task
methods so the calling source does not have fetch a trace
directly from the Tracer
new API for getting the current trace's headers. Also a
standardized naming convention for the trace header names
so the same can be used when intiializing a trace with
parent trace/span info
cleaned up zephyr and tracer a bit
Ugh - no choice for now but to tie sweatshop
to our internal implementation. Will get the internal sweatshop
to sync with the OSS version soon
All tests passing again