Add unique <title> tag to each page

[oneezy]

In the Polymer Shop app, a unique <title> tag was added for each page.

I think it would be beneficial to add the same functionality to the PSK.

[jsilvermist]

Agreed, I did this in PSK 1, but using a slightly hacky method since without using a setTimeout call in the page.js page callback it would change the title before calling pushState.

[oneezy]

Here's the commit that was added in the Shop app for this,
https://github.com/Polymer/shop/pull/32/files