Support IE8+ via HTML5-History-API polyfill

This patch gets page.js working when polyfilled with @devote's [history polyfill](https://github.com/devote/HTML5-History-API) in IE8 + 9. Solves (more or less) #5.

The tests don't even begin to run in IE, but passes elsewhere, and it passes all my tests on my [Meteor Router](https://github.com/tmeasday/meteor-router). See https://github.com/tmeasday/meteor-router/issues/33 for more information. Haven't had much of a play outside of that context, but my understanding is that it works.