fix linting in domain.js
run with code coverage in npm test
disable report for spawned processes
test stdout & stderr
test invalid backupFile
add istanbul ignores for untestable code
enforce pre commit tests
Add a test for 100% code coverage.

I recently landed a PR for new features without adding tests.
This is bad. The tests & tooling should shout at me for this.

cc @dfellis thanks for teaching me this trick.
use english
i meant 100% branch coverage
Merge pull request #5 from uber/better-tests

Fix test debt from stdout/stderr PR