fix(urlRouter): html5Mode accepts an object from angular v1.3.0-rc.3

Since https://github.com/angular/angular.js/commit/dc3de7fb7a14c38b5c3dc7decfafb0b51d422dd1 angular
accepts both boolean and objects like {enabled: true, requireBase: false} causing the evaluation to be
always true. In order to allow the use of ui-router with angular 1.3 a fix has been made, it checks
if the value is an object and gets its enabled property value.

Fixes https://github.com/angular-ui/ui-router/issues/1397