chore(code clean-up): optimize propsFilter

Move ‘var keys = Object.keys(props);’ outside of the items.forEach(…)
loop. As previously written, keys will be re-instantiated on every
iteration of the forEach loop.

Author: haroldcampbell

examples/demo.js

@@ -13,10 +13,11 @@ app.filter('propsFilter', function() {
     var out = [];
 
     if (angular.isArray(items)) {
+      var keys = Object.keys(props);
+        
       items.forEach(function(item) {
         var itemMatches = false;
 
-        var keys = Object.keys(props);
         for (var i = 0; i < keys.length; i++) {
           var prop = keys[i];
           var text = props[prop].toLowerCase();