On search page, push to history when user stops typing

[eddieantonio]

Makes the behaviour of the back button a bit more intuitive. Basically, when a user has finished typing a query, views some results, then types a different query, they expect that to be two different search results. However, if you don't navigate away from the search results, it all looks like one state in history. So there should be some heuristic that states, "user is looking at the results and no longer typing".