feat(autocomplete): allow disabling asterisk on floating label

Closes #7119

src/components/autocomplete/autocomplete.spec.js

@@ -1061,6 +1061,25 @@ describe('<md-autocomplete>', function() {
       expect(ctrl.isRequired).toBe(true);
     });
 
+    it('should forward the md-no-asterisk attribute', function() {
+      var scope = createScope();
+      var template = '\
+          <md-autocomplete\
+              md-selected-item="selectedItem"\
+              md-search-text="searchText"\
+              md-items="item in match(searchText)"\
+              md-item-text="item.display"\
+              md-min-length="0" \
+              required\
+              md-no-asterisk="true"\
+              md-floating-label="Asterisk Label">\
+            <span md-highlight-text="searchText">{{item.display}}</span>\
+          </md-autocomplete>';
+      var element = compile(template, scope);
+      var input = element.find('input');
+
+      expect(input.attr('md-no-asterisk')).toBe('true');
+    });
   });
 
   describe('md-highlight-text', function() {

src/components/autocomplete/js/autocompleteDirective.js

@@ -52,6 +52,7 @@ angular
  * @param {boolean=} md-autofocus If true, the autocomplete will be automatically focused when a `$mdDialog`,
  *     `$mdBottomsheet` or `$mdSidenav`, which contains the autocomplete, is opening. <br/><br/>
  *     Also the autocomplete will immediately focus the input element.
+ * @param {boolean=} md-no-asterisk When present, asterisk will not be appended to the floating label
  * @param {boolean=} md-autoselect If true, the first item will be selected by default
  * @param {string=} md-menu-class This will be applied to the dropdown menu for styling
  * @param {string=} md-floating-label This will add a floating label to autocomplete and wrap it in
@@ -244,6 +245,7 @@ function MdAutocomplete () {
                   ng-model="$mdAutocompleteCtrl.scope.searchText"\
                   ng-keydown="$mdAutocompleteCtrl.keydown($event)"\
                   ng-blur="$mdAutocompleteCtrl.blur()"\
+                  ' + (attr.mdNoAsterisk != null ? 'md-no-asterisk="' + attr.mdNoAsterisk + '"' : '') + '\
                   ng-focus="$mdAutocompleteCtrl.focus()"\
                   aria-owns="ul-{{$mdAutocompleteCtrl.id}}"\
                   ' + (attr.mdSelectOnFocus != null ? 'md-select-on-focus=""' : '') + '\