$apply vs $digest

https://www.sitepoint.com/understanding-angulars-apply-digest/

remove hash

https://scotch.io/tutorials/pretty-urls-in-angularjs-removing-the-hashtag
http://www.getursolution.com/2016/06/15/angularjs-pretty-url-remove-hash/

angular js deep linking

http://odetocode.com/blogs/scott/archive/2014/04/14/deep-linking-a-tabbed-ui-with-angularjs.aspx