* fix test coverage.
* changes per comments + added test-coverage script to increase max-old-space-size of V8
ref: https://nodejs.org/api/cli.html#cli_max_old_space_size_size_in_mbytes
* renamed test:coverage and test:debug.
* circle-ci to use test:coverage.
* reduced test coverage thresholds.
Co-authored-by: Andrew Henry <akhenry@gmail.com>
