cli: create writeFile destination if necessary

[servusdei2018]

Summary
This PR introduces a fix for writeFile. The function currently assumes that the directories leading to the specified filePath exist, but this PR ensures that they exist.

Related Issues/PRs
No related issues or PRs.

[adamraine]

Hmm looks like the "throws for invalid paths" test case is failing because !/#@.json is now a valid path (at least on my mac, and our windows CI job).

This updated test should cover the new logic:

it('throws for invalid paths', () => {
  const path = '//#@.json';
  const report = JSON.stringify(sampleResults);
  return assert.rejects(Printer.write(report, 'html', path));
});

[adamraine]

Please remove the yarn.lock and package-lock.json changes