Add newer Node.js versions for prebuilt binaries

[ShinySaana]

Audify is behind 2 major version releases for Node, both in "classic" Node and electron-node, which can impact projects which rely on those. This simple patch should add those newer versions to the batch of binaries that are built for each releases.

[almoghamdani]

I don't see a reason why the Node.js that is installed on the build machine should be the latest and not LTS (which should be more stable)
This should not affect building for newer/older Node.js versions (since cmake-js downloads the correct lib/headers for each version and links against it - therefore not related to the installed node.js)

[almoghamdani]

Also, please update the README with the new supported versions for prebuilts

[ShinySaana]

(since cmake-js downloads the correct lib/headers for each version and links against it - therefore not related to the installed node.js)

I didn't know that, modifying this right away

[ShinySaana]

For some unknown reason, Travis failed for the first commit but passed fine for the following, so I believe it's ready now!

[ShinySaana]

Okay so the build crashed on master, and by looking the travis builds, my first guess would because of artifact caching between builds, and that we indeed need the latest version and not the LTS one