This demo shows an example of using Polymer to create a web component with simple markup, where the complexity is abstracted away to an externally located resource. Here's how it works:
The webcomponents polyfill script is included in the head of the page.
The custom component is imported (in this case from an external domain) using a link rel="import" in the document head:
All of the logic and presentation around the "github-commits" element is contained in the imported component, including css, script and markup. (View source of github-commits.html for full code).