Automate component version updates

[arthurevans]

Currently the polymer components in the tutorial repo are updated manually (bower update, git commit & git push). From the website, we link people to the zip download of the tutorial repo.

Could we automate this somehow?

One dependency to keep in mind: the website pulls the tutorial repo and vulcanizes the finished version o f the tutorial so we can show a demo of the app. If we change how the tutorial repo is structured, we might need to update the website build process.
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