If tagging mode is activated, do not check values

Motivation: Fix #540
The tagging mode is designed to allow new values to be added to the model.
It does not make sense to check those values against the list of choices when going from model --> view.

Author: Asimov4

src/select.js

@@ -991,6 +991,7 @@
                 return false;
               };
               if (!inputValue) return resultMultiple; //If ngModel was undefined
+              if ($select.tagging.isActivated) return inputValue; // If tagging is enabled, preserve model values
               for (var k = inputValue.length - 1; k >= 0; k--) {
                 if (!checkFnMultiple($select.selected, inputValue[k])){
                   checkFnMultiple(data, inputValue[k]);

test/select.spec.js

@@ -1668,6 +1668,26 @@ describe('ui-select tests', function() {
 
       expect(el.scope().$select.multiple).toBe(true);
     });
+    
+    it('should preserve the model if tagging is enabled on select multiple', function() {
+      scope.selection.selectedMultiple = ["I am not on the list of choices"];
+
+      var el = compileTemplate(
+          '<ui-select multiple="multiple" tagging ng-model="selection.selectedMultiple" theme="bootstrap" style="width: 800px;"> \
+              <ui-select-match placeholder="Pick one...">{{$item.name}} &lt;{{$item.email}}&gt;</ui-select-match> \
+              <ui-select-choices repeat="person.email as person in people | filter: $select.search"> \
+                <div ng-bind-html="person.name | highlight: $select.search"></div> \
+                <div ng-bind-html="person.email | highlight: $select.search"></div> \
+              </ui-select-choices> \
+          </ui-select> \
+          '
+      );
+
+      scope.$digest();
+
+      expect(scope.selection.selectedMultiple)
+         .toEqual(["I am not on the list of choices"]);
+    });
 
     it('should allow paste tag from clipboard', function() {
        scope.taggingFunc = function (name) {