feat($browser): jQuery style url method, onUrlChange event

This is just basic implementation of $browser.url, $browser.onUrlChange methods:

$browser.url() - returns current location.href

$browser.url('/new') - set url to /new
If supported, history.pushState is used, location.href property otherwise.

$browser.url('/new', true) - replace current url with /new
If supported, history.replaceState is used, location.replace otherwise.

$browser.onUrlChange is only fired when url is changed from the browser:
- user types into address bar
- user clicks on back/forward button
- user clicks on link

It's not fired when url is changed using $browser.url()

Breaks Removed $browser.setUrl(), $browser.getUrl(), use $browser.url()
Breaks Removed $browser.onHashChange(), use $browser.onUrlChange()