* Update License header for all source files
- Add Apache 2.0 header to source files that did not have one.
- Update all existing headers dated to 2019 to be 2020
- Remove comma from License header to comply with the Apache 2.0
guidelines.
* Update Copyright notice
Use the standard Copyright notices outlined by the
[CNCF](https://github.com/cncf/foundation/blob/master/copyright-notices.md#copyright-notices)
Tracer.WithSpan() will now accept StartOptions as a variadic final parameter `opts`
that will be passed to the Tracer.Start() invocation that creates the Span
wrapping the user-provided function.
Change all occurrences of value to pointer receivers
Add meta sys files to .gitignore
Code cleanup e.g.
- Don't capitalize error statements
- Fix ignored errors
- Fix ambiguous variable naming
- Remove unnecessary type casting
- Use named params
Fix#306
* Make span start/end configuration more greppable
Rename SpanOption to StartOption
Rename StartOptions to StartConfig
Rename EndOptions to EndConfig
fixes#197
* move bridge out of the experimental directory
* drop a leftover from experimental stuff in gitignore
found by accident when doing `git grep experimental`.