Text input that converts between a delimited string and an array of strings. The default
delimiter is a comma followed by a space - equivalent to `ng-list=", "`. You can specify a custom
delimiter as the value of the `ngList` attribute - for example, `ng-list=" | "`.
The behaviour of the directive is affected by the use of the `ngTrim` attribute.
* If `ngTrim` is set to `"false"` then whitespace around both the separator and each
  list item is respected. This implies that the user of the directive is responsible for
  dealing with whitespace but also allows you to use whitespace as a delimiter, such as a
  tab or newline character.
* Otherwise whitespace around the delimiter is ignored when splitting (although it is respected
  when joining the list items back together) and whitespace around each list item is stripped
  before it is added to the model.
### Example with Validation
<example name="ngList-directive" module="listExample">
  <file name="app.js">
     angular.module('listExample', [])
       .controller('ExampleController', ['$scope', function($scope) {
         $scope.names = ['morpheus', 'neo', 'trinity'];
       }]);
  </file>
  <file name="index.html">
   <form name="myForm" ng-controller="ExampleController">
     <label>List: <input name="namesInput" ng-model="names" ng-list required></label>
     <span role="alert">
       <span class="error" ng-show="myForm.namesInput.$error.required">
       Required!</span>
     </span>
     <br>
     <tt>names = {{names}}</tt><br/>
     <tt>myForm.namesInput.$valid = {{myForm.namesInput.$valid}}</tt><br/>
     <tt>myForm.namesInput.$error = {{myForm.namesInput.$error}}</tt><br/>
     <tt>myForm.$valid = {{myForm.$valid}}</tt><br/>
     <tt>myForm.$error.required = {{!!myForm.$error.required}}</tt><br/>
    </form>
  </file>
  <file name="protractor.js" type="protractor">
    var listInput = element(by.model('names'));
    var names = element(by.exactBinding('names'));
    var valid = element(by.binding('myForm.namesInput.$valid'));
    var error = element(by.css('span.error'));
    it('should initialize to model', function() {
      expect(names.getText()).toContain('["morpheus","neo","trinity"]');
      expect(valid.getText()).toContain('true');
      expect(error.getCssValue('display')).toBe('none');
    });
    it('should be invalid if empty', function() {
      listInput.clear();
      listInput.sendKeys('');
      expect(names.getText()).toContain('');
      expect(valid.getText()).toContain('false');
      expect(error.getCssValue('display')).not.toBe('none');
    });
  </file>
</example>
### Example - splitting on newline
<example name="ngList-directive-newlines">
  <file name="index.html">
   <textarea ng-model="list" ng-list="&#10;" ng-trim="false"></textarea>
   <pre>{{ list | json }}</pre>
  </file>
  <file name="protractor.js" type="protractor">
    it("should split the text by newlines", function() {
      var listInput = element(by.model('list'));
      var output = element(by.binding('list | json'));
      listInput.sendKeys('abc\ndef\nghi');
      expect(output.getText()).toContain('[\n  "abc",\n  "def",\n  "ghi"\n]');
    });
  </file>
</example>