Anchor scroll offset

Just talked to @IgorMinar:
Let's make this a helper function in `jqLite.js` but not add it to jqLite / jQuery prototype, like so:

```
// Note: This is a private method that should not be exposed
// unto jQLitePrototype
function jQLiteReadyLoaded(trigger, win) {
  win = win || window;
  if (win.document.readyState === 'complete') {
    trigger();
  } else {
    // Note: No need to unregister as `load` fires only once.
    // See jqLite.ready...
    jqLite(win).on('load', trigger);
  }
}
```

The tests for this method would pass in a fake `$window`.

In the tests for `$anchorScroll` we would do the following:

```
var oldJQLiteReadyLoaded;
beforeEach(function() {
  oldJQLiteReadyLoaded = window.jQLiteReadyLoaded;
  window.jQLiteReadyLoaded = jasmine.createSpy('jQLiteReadyLoaded');
});
afterEach(function() {
  window.jQLiteReadyLoaded = oldJQLiteReadyLoaded
});
```

This works as during unit tests we don't add the function closure of angular and all privates are accessible on the `window.