* fix compile errors.
* fix lint errors.
* add circle-ci job.
* rename IDHigh to TraceIDHigh
* rename the file.
* add go get for goimports and golangci-lint
* enable GO111MODULE and remove comments.
* remove working dir and update cache name
* Add TEST_RESULT env back.
* run go mod tidy.
* remove go mod download.
* add test coverage.
* fix TraceID.
* fix circlefi config error.
* remove install-tools.
* remove ALL_TEST_SRC from Makefile.
* rename Log and Logf interface to AddEvent and AddEventf.
- also remove log package.
* provide only AddEvent interface to Span
- Event can be created using Event specific interface.
* add var trick for Event interface.
