Preserve url fragment on page reload

This fixes a bug where the URL hash disappears when a page is first loaded.

For instance, if you had a link `<a href="#someanchor">link</a>` on your page and clicked on it, the link would work correctly (it would scroll to `#someanchor`), but if you copied and pasted the URL into a new tab and navigated to the page afresh, the hash would disappear and no scrolling would occur.

See also: https://github.com/angular-ui/ui-router/issues/510