make highlight filter work with numeric query (fix #1400)

src/common.js

@@ -135,7 +135,7 @@ var uis = angular.module('ui.select', [])
  */
 .filter('highlight', function() {
   function escapeRegexp(queryToEscape) {
-    return queryToEscape.replace(/([.?*+^$[\]\\(){}|-])/g, '\\$1');
+    return ('' + queryToEscape).replace(/([.?*+^$[\]\\(){}|-])/g, '\\$1');
   }
 
   return function(matchItem, query) {

test/select.spec.js

@@ -2328,6 +2328,13 @@ describe('ui-select tests', function() {
 
       expect(highlight(item, query)).toBe('20<span class="ui-select-highlight">15</span>');
     });
+
+    it('properly works with numeric queries', function() {
+      var query = 15;
+      var item = 2015;
+
+      expect(highlight(item, query)).toBe('20<span class="ui-select-highlight">15</span>');
+    });
   });
 
 });