Automatic NPM publish via Travis

In my last post, I had written about updating the grunt plugins that I use to the latest version of Grunt. As this issue suggests, I try to keep updating my code, but almost always forget to update the version on the npm registry.
Since npm itself it a package that can be used programmatically, I decided to automate the process such that a new version is published to the npm registry every time a new package version is built successfully in the continuous integration system. Technically, it just had to be a npm publish from Travis. Note that since Travis does not preserve states between runs, there would be no ~/.npmrc and I would have to add user every time. Since travis supports adding secure environment variables, I could use that to pass the values passed to adduser using this.
I started looking at the node-publish package as it was the easiest way to push code from a CI system. Everything seemed to work well on my local system, but publishing from Travis failed. After digging through the code of npm, npm-commands and npm-registry, I noticed that npm.registry.addUser only authenticates the user and sets the user name and password in the config. It does not set the email, which is required by the publish method. I have submitted a pull request to node-publish that adds the email to the npm.config, and this fixed publish to run on Travis too.
Till the pull request gets accepted, I am using the raw npm methods to authenticate and publish to the registry. It does not have the version checking logic in npm-publish, but I can live with that as versions are not overwritten and all versions that do not exist in the npm registry (new or old) do get updated. Here is the simple code to update npm packages from travis, without the hassels of ~/.npmrc.
Note that the credentials are supplied by the environment, and as mentioned earlier, should be encrypted.