Add replaceState support

[ralphsmith80]

I'm using a setTimeout in .to so the path will resolve before forwarding to another route. This maybe the reason the add delay() issue was filed since that's what I started investigating before I realized the behavior I want to achieve is supported by IE10+ browsers with history.replaceState.

Example:

Path.map('/app').to(function() {
  // timeout is set so that the `history.pushState` happens before we navigate to the route we want
  // to redirect to https://github.com/mtrpcic/pathjs/blob/master/path.js#L21
  setTimeout(function() {
    var id = '1234';
    Path.history.pushState({}, null, '/app/'+id);
  }, 0);
});
Path.map('/app/:id').to(function() {
  // do stuff with a view that require an id, i.e. this.params.id
});

Using the setTimeout is functionally correct but if I use the back button I would go back to /app which would just forward me back to /app/1234. If I use replaceState then I replace history with the correct url so the back button functions how a user would expect it to.

Basically a redirect that is opaque to the user so we shouldn't keep that in history. i.e. use history.replaceState.