Implement scripts to collect coverage reports (JSON format) from all packages
in the monorepo that generate such reports. Reports are copied to
`<root>/.nyc_output/coverage-[pkg-dir-name].json`.
Implement scripts to generate a combined html report in `<root>/coverage`.
Adjust root `reset` and `clean` scripts to delete `<root>/.nyc_output` and
`<root>/coverage`.
Implement a script in `<root>/package.json` to generate a `text-lcov` report
and upload it to coveralls from CI builds. Remove coveralls from
`packages/embark`.
Supply `packages/embark` with an nyc configuration in its `package.json` and
have its `"test":` script generate both `json` and `html` reports.
Use nyc with `embarkjs`'s test suite: supply an nyc configuration in its
`package.json` and have its `"test":` script generate both `json` and `html`
reports.
Adjust `embarkjs`'s tests for more accurate coverage reporting.