Generated htmlmin task produces confusing, redundant index.html

[jyasskin]

The default output of yo polymer includes a vulcanize task that generates build.html, and an htmlmin task that copies over index.html. The compiled application definitely doesn't need both, and I was confused when I redirected the vulcanize output to index.html and it got overwritten by the htmlmin output.

[robdodson]

This should be resolved in the latest release. We now vulcanize all elements into elements.vulcanized.html and don't touch index.html.