title: Angular $filter is filtering negative numbers even though the filter is a positive number
body: <p>I have a simple filter for a array. each item in the array has a 'Rating' attribute that is a number. The values can be -3,-2,-1,1,2,3.</p>
  
  <p>If I do </p>
  
  <p><code>$scope.ratingFilter = -3; // negative numbers work fine</code></p>
  
  <p>BUT if I do</p>
  
  <p><code>$scope.ratingFilter = 3; // positive numbers are showing items that have a Rating of 3 AND -3. Why are negative number appearing in the filter???</code></p>
  
  <pre><code>$scope.updateMarkers = function(){
  
      var filters = [];
      if($scope.ratingFilter != 'all'){
          filters.Rating = $scope.ratingFilter;
      }
  
      var arr = [];
      angular.forEach($scope.allMarkers, function(value, key){
          arr.push(value);
      });
  
      $scope.markers = $filter('filter')(arr, filters);
  }
  </code></pre>