title: Add dropdown menu inside sidebar with material design?
body: <p>I would like when click on polls , open dropdown menu which include sub categories of pulls. </p>
  
  <p><img src="https://i.stack.imgur.com/3FPg2.jpg" alt="enter image description here"></p>
  
  <p>How i should change my code in order to add this functionality with material design.</p>
  
  <p>In state provider:</p>
  
  <pre><code> $stateProvider
         .state('admin', {
          /*abstract: true,*/
          url: '/admin',
          templateUrl: 'app/admin/admin.html',
          controller: 'AdminCtrl',
          onEnter: function($rootScope) {
          $rootScope.title = $rootScope.titleRoot + ' | Admin';
          }
        });
    });
  </code></pre>
  
  <p>and in .html</p>
  
  <pre><code>&lt;md-sidenav class="md-sidenav-left md-whiteframe-z2" md-component-id="left" md-is-locked-open="$mdMedia('gt-md')"&gt;
      &lt;md-toolbar class="md-theme-indigo"&gt;
        &lt;h1 class="md-toolbar-tools"&gt;Admin&lt;/h1&gt;
      &lt;/md-toolbar&gt;
      &lt;md-content class="" ng-controller="LeftCtrl"&gt;
        &lt;md-button ng-click="close()" class="md-primary" hide-gt-md&gt;
          Close Sidenav Left
        &lt;/md-button&gt;
        &lt;!--&lt;p hide-md show-gt-md&gt;--&gt;
        &lt;!--&lt;/p&gt;--&gt;
        &lt;ul class="sidenav-menu"&gt;
          &lt;li class="" ng-repeat="section in sections"&gt;
  
            &lt;md-button ui-sref="{{section.link}}"&gt;
              &lt;i class="fa fa-fw {{section.icon}}"&gt;&lt;/i&gt; {{section.title}}
            &lt;/md-button&gt;
  
          &lt;/li&gt;
        &lt;/ul&gt;
      &lt;/md-content&gt;
    &lt;/md-sidenav&gt;
  </code></pre>
  
  <p>Inside Controller:</p>
  
  <pre><code>.controller('AdminCtrl', function($scope, $mdSidenav, $timeout, $log) {
      $scope.sections = [
        {
          title: 'User Management',
          icon: 'fa-user',
          link: 'usermanagement'
        },{
          title: 'Polls',
          icon: 'fa-files-o',
          link: 'polls'
        }    
      ];    
      $scope.toggleLeft = function () {
        $mdSidenav('left').toggle()
          .then(function () {
            //$log.debug("toggle left is done");
          });
      };
    })
    .controller('LeftCtrl', function($scope, $timeout, $mdSidenav, $log) {
      $scope.close = function() {
        $mdSidenav('left').close()
          .then(function(){
            //$log.debug("close LEFT is done");
          });
      };
    });
  </code></pre>