Fix ability to pass TracingEventReceiver to dbr (gocraft#154)

* add failing tests that exercise TracingEventReceiver

* pass EventReceiver explicitly between types rather than embedded parent struct

* Code review comments for gocraft#154

* address code review comments for gocraft#154

HOUSEKEEPING: add stale bot

TEST: upgrade to circleci 2.0 (gocraft#126)

Merge branch 'TC_2.1'

FEATURE: 2.0

tl;dr
1. postgres
2. support almost all common sql statements
3. modularize syntax support for extensibility
4. compatible with 1.0

Merge pull request gocraft#17 from philips/getting-started-fix

README: add encoding/json to getting started