feat($location): add support for state and title in pushState

This is a continuation of #3325, re-created per my e-mail thread with @IgorMinar.

Adds $location pushState & replaceState methods acting as proxies to history
pushState & replaceState methods. This allows using pushState to change state
and title as well as URL. Note that these methods are not compatible with
browsers not supporting the HTML5 History API, e.g. IE 9.
@IgorMinar IIRC this `if` was originally meant to prevent infinite digest in IE9 in hash mode. I added comparing states, I could also check `title` (though browsers don't expose the `title` param used in `pushState` in any way) but I'm not sure if it's needed in HTML5 mode?