Add History.pushState

[xeoncross]

We should have a simple History.pushState method for new browsers wthat could load the new page via-AJAX and then gracefully replace the content and update the URL.

[aravindet]

Since the entire file would have to be loaded via AJAX, the primary motivation for doing this (reducing page size) is gone. What advantage would this provide, and is it worth the complexity?

[xeoncross]

Actually, there are two things this would help with. First, using History.pushState would increase the page render time as the DOM would not re-render the entire chrome. Second, it would remove the FOUC a new page load might still have even with the caching we are doing.

We only need to implement this for modern browsers (the only people who even care about FOUC) so the code to implement this shouldn't be more than a few dozen lines.