On each commit that passes through Travis, the travis_publish.sh script checks for the string [publish binary] in the commit message, and if present, runs node-pre-gyp publish to publish a binary.
Running npm publish doesn't actually upload a binary anywhere, but instead just pushes up your local code with an updated version number in package.json. When your module is installed with npm install, node-pre-gyp will use this version number to search for a published binary, falling back to a source compile if no matching binary is found.
Typical workflow:
git checkout master
# increment version number
# https://docs.npmjs.com/cli/version
npm version major | minor | patch
# amend commit to include "[publish binary]"
git commit --amend
"x.y.z" -> "x.y.z [publish binary]"
# push commit and tag to remote
git push
git push --tags
# make a sandwich, check travis console for build successes
# test published binary (should install from remote)
npm install && npm test
# publish to npm
npm publish