* WIP
* Finish http middleware implementation
This is currently done as httptrace.NewHandler(). This should maybe
be moved to a different package or renamed, but atm this name
seemed the least objectionable to me.
There are a few TODOs sprinkled in the code for questions I didn't
know the answers to.
There is an example provided, which when copied to a main func
locally work against the jaeger all in one.
Real tests need to be added.
* Address feedback
* Tie in propagation, update attributes, more options, revise example, etc.
Dropped the httpConfig type because it seemed redundant an unecessary
abstraction.
* WithRouteTag
* address out of band feedback
* move to othttp package
* Add a very basic test.
I ended up needing to export the Traceparentheader const so that
it was accessible to this test.
* Add file header
