Add back node-gyp dependency

[winstliu]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

Reverts most of #832. There's been a few problems with node-gyp being unable to find dependencies or rebuilding failing on 32-bit Windows, which I think may be resolved if we simply go back to depending on it explicitly. I have, however, updated the dependency to match that of npm@6.2.0.

Alternate Designs

#832, which was causing flaky builds on this repo and rebuild errors downstream in atom/atom.

Benefits

Newer node-gyp version (VS2017 support, bugfixes, etc).

Possible Drawbacks

We'll have to remember to update node-gyp each time we update npm.

Verification Process

N/A

Applicable Issues

#832, atom/atom#19189