* Provide conformance tests for tracers
The test harness may be used to ensure that a given tracer behaves
according to the expectations set by the API.
* Add `ToMatchError` matcher
* Use DeepEqual to compare unknown types in matchers
Unlike basic `==`/`!=`, `reflect.DeepEqual` can compare arbitrary
types (e.g., `[]string` to `[]string`)
* Use struct instead of string for test context key
Since these methods are about the span itself rather than specifically
*events* on the span, it makes sense to drop "events" from their names.
[Closes#33]
* setup sdk exporter package
* use sdk exporter package in sdk trace
* use sdk exporter package in all exporters
* empty the exporters list before testing Load
* move SpanData to the exporter package
* use the SpanProcessor registration, don't register exporters
* rename exporter structs to avoid stutter
* rename Syncer and Batcher to SpanSyncer and SpanBatcher
So it's explicit they are for spans, and we reduce the risk of name
conflict
* remove not moot todo
* rename sdk exporter to export
* only execute the SpanData if it is sampled
* rename finish -> end
* missed a few finish -> end spots
* change end back to finish for the bridge span in the openTracing bridge
* fixed grammar, ran make
* Merge two event methods in span API
There was an agreement to get rid of the Event interface and
consolidate the two methods for adding events into one. See #57.
* Eliminate the use of the Event interface
There is no need for the SDK to provide the implementation of the
Event interface - it is used nowhere.
* Drop the Event interface
It's dead code now.
* Make it possible to override a finish timestamp through options
Opentracing to opentelemetry bridge will certainly use this feature.
* Obey the start time option
* Add tests for events and custom start/end times
* trace sdk initial commit.
* fix imports and comments.
* remove tracestate
* split trace.go
* add attribute over limit test.
* add comments and restructure span.go and tracer.go
* refactor MessageEvent
* defer unlock
* some more cleanup in span.go
* rename *MessageEvent* to *Event*
* cleanup comments in trace_test.go
* fix typos.
* return full string ID for traceID and spanID.
