build: add a test-ci task, quieten npm
logging: safer logging on errors.
logging: lowered urgency of instrumentation lgoging

We can use this information, but it's not worth bothering end-user
developers with.
code: got rid of gratuitous event
agent: add tests for error merging

Turns out the conditionals were inside-out, so it's a good thing I added
these tests!
environment: do not crash on bad NODE_PATH env var
test: environment scraper should not crash from bad NODE_PATH
code: jshint & style tweaks
instrumentation: 1.3.20 introduces a new Scope
tests: fixed unit tests with child process
code: style tweaks
docs: added security policy
docs: add filing a low-detail GitHub issue
test: confirm the absence of an expected throw
test: cleanup

Also the error tracer no longer uses domains, so eliminate that test.
errors: remove dominion

Instead modify the CLS async listener to include an error tracer. Unit
tests are all passing, and the two integration tests that are failing
highlight behavior in CLS that requires some analysis to properly
address.

The new strategy creates significantly fewer objects and is measurably
faster, just running the tests. If we can figure out how to make it
work, we will have a major win.
instrumentation: ensure transaction is in scope
tracer: use latest CLS API.
tracer: make responsible for segment management
tracer: State.prototype.getTransaction is obsolete