Clear npm audit vulnerabilities

[darshan-Jahagirdar]

Fixes #40.

The package already declares mongodb ^3.3.3, but the lockfile still resolved vulnerable transitive packages, including bson@1.1.1. This refreshes the lockfile to patched bson@1.1.6, updates the pinned Vows dev dependency to 0.8.3 so the full audit is clean, and changes the test script from node node_modules/.bin/vows to vows so it invokes the cross-platform npm shim.

Bounty: targets the $20 Bountysource bounty linked from #40.

Verification:

• npm install
• npm audit --json reports 0 vulnerabilities
• npm test now invokes vows correctly, then stops because this checkout does not include test/db.config.json / a MongoDB service for the integration suite.
• git diff --cached --check passed before commit.

[darshan-Jahagirdar]

Validation update for this PR:

npm audit --audit-level=high
git diff --check

Result: npm audit reports 0 vulnerabilities, and the diff whitespace check passed locally.

I also checked the test command earlier; npm test requires test/db.config.json and a MongoDB test service, which are not present in this local environment, so I did not treat that as a reliable local signal.