feat(select): add md-container-class for custom styling

closes #3116

src/components/select/select.js

@@ -45,6 +45,7 @@ angular.module('material.components.select', [
  * @param {expression=} md-on-close expression to be evaluated when the select is closed
  * @param {string=} placeholder Placeholder hint text.
  * @param {string=} aria-label Optional label for accessibility. Only necessary if no placeholder or
+ * @param {string=} md-container-class class list to get applied to the .md-select-menu-container element (for custom styling)
  * explicit label is present.
  *
  * @usage
@@ -336,6 +337,7 @@ function SelectDirective($mdSelect, $mdUtil, $mdTheming, $mdAria, $interpolate,
         selectEl.data('$mdSelectController', mdSelectCtrl);
         selectScope = scope.$new();
         $mdTheming.inherit(selectContainer, element);
+        selectContainer[0].setAttribute('class', selectContainer[0].getAttribute('class') + ' ' + element.attr('md-container-class'));
         selectContainer = $compile(selectContainer)(selectScope);
         selectMenuCtrl = selectContainer.find('md-select-menu').controller('mdSelectMenu');
       }

src/components/select/select.spec.js

@@ -113,6 +113,14 @@ describe('<md-select>', function() {
     expect(select.attr('aria-disabled')).toBe('true');
   }));
 
+  it('supports passing classes to the container', inject(function($document) {
+    var select = setupSelect('ng-model="val", md-container-class="test"').find('md-select');
+    openSelect(select);
+    var container = $document[0].querySelector('.md-select-menu-container');
+    expect(container).toBeTruthy();
+    expect(container.classList.contains('test')).toBe(true);
+  }));
+
   it('closes the menu if the element is destroyed', inject(function($document, $rootScope) {
     var called = false;
     $rootScope.onClose = function() {