feat(formatter): Add arrayify formatter.

MapFormatter can be used with map and ng-repeat to display a list of key value pairs

Closes #394

Closes #931

lib/formatter/arrayify.dart

@@ -0,0 +1,27 @@
+part of angular.formatter_internal;
+
+/**
+ * Given a Map, returns a list of items which have `key` and `value` property.
+ *
+ * Usage:
+ *
+ *     <div ng-repeat="item in {'key1': 'value1', 'key2':'value2'} | arrayify">
+ *       {{item.key}}: {{item.value}}
+ *     </div>
+ */
+@Formatter(name:'arrayify')
+class Arrayify implements Function {
+  List<_KeyValue> call(Map inputMap) {
+    if (inputMap == null) return null;
+    List<_KeyValue> result = [];
+    inputMap.forEach((k, v) => result.add(new _KeyValue(k, v)));
+    return result;
+  }
+}
+
+class _KeyValue<K, V> {
+  K key;
+  V value;
+
+  _KeyValue(this.key, this.value);
+}

lib/formatter/module.dart

@@ -29,6 +29,7 @@ export "package:angular/formatter/module_internal.dart" show
     Json,
     LimitTo,
     Lowercase,
+    Arrayify,
     Number,
     OrderBy,
     Uppercase,

lib/formatter/module_internal.dart

@@ -13,13 +13,15 @@ part 'filter.dart';
 part 'json.dart';
 part 'limit_to.dart';
 part 'lowercase.dart';
+part 'arrayify.dart';
 part 'number.dart';
 part 'order_by.dart';
 part 'uppercase.dart';
 part 'stringify.dart';
 
 class FormatterModule extends Module {
   FormatterModule() {
+    type(Arrayify);
     type(Currency);
     type(Date);
     type(Filter);

test/angular_spec.dart

@@ -215,6 +215,7 @@ main() {
         "angular.formatter_internal.Json",
         "angular.formatter_internal.LimitTo",
         "angular.formatter_internal.Lowercase",
+        "angular.formatter_internal.Arrayify",
         "angular.formatter_internal.Number",
         "angular.formatter_internal.OrderBy",
         "angular.formatter_internal.Stringify",

test/formatter/arrayify_spec.dart

@@ -0,0 +1,18 @@
+library map_spec;
+
+import '../_specs.dart';
+import 'package:angular/formatter/module.dart';
+
+void main() {
+  describe('arrayify', () {
+    it('should convert a map to list of key value pairs', (Parser parse, FormatterMap formatters) {
+      List result = parse('{"key1": "value1", "key2": "value2"} | arrayify').eval(null, formatters);
+      expect(result.map((kv) => kv.key)).toEqual(["key1", "key2"]);
+      expect(result.map((kv) => kv.value)).toEqual(["value1", "value2"]);
+    });
+
+    it('should treat null as noop', (Parser parse, FormatterMap formatters) {
+      expect(parse('null | arrayify').eval(null, formatters)).toEqual(null);
+    });
+  });
+}