Use Github Releases for hosting node binaries (#6030)

* Use Github Releases for hosting node binaries

Replaces S3 hosting of node binaries with Github Releases.
`node-pre-gyp publish` works exclusively with S3, so upload step
is now performed by the Travis deployment provider.

The behaviour for the package user should not change.
When building a new version tag, Travis will create a release for the
tag if it does not already exist.

* Switch to the osrm-release-automation machine account rather than personal credentials.

Co-authored-by: Daniel Patterson <danpat@danpat.net>

scripts/travis/node_package.sh

@@ -31,7 +31,7 @@ if [[ ${PUBLISH} == 'On' ]]; then
         fi
     fi
 
-    ./node_modules/.bin/node-pre-gyp package publish info $NPM_FLAGS
+    ./node_modules/.bin/node-pre-gyp package testpackage $NPM_FLAGS
 else
     echo "PUBLISH is set to '${PUBLISH}', skipping."
 fi