added _.forIn definition

lodash/lodash-tests.ts

@@ -554,6 +554,18 @@ result = <string>_.findLastKey({ 'a': 1, 'b': 2, 'c': 3, 'd': 4 }, function(num)
   return num % 2 == 1;
 });
 
+function Dog(name) {
+  this.name = name;
+}
+
+Dog.prototype.bark = function() {
+  console.log('Woof, woof!');
+};
+
+_.forIn(new Dog('Dagny'), function(value, key) {
+  console.log(key);
+});
+
 var mergeNames = {
   'stooges': [
     { 'name': 'moe' },

lodash/lodash.d.ts

@@ -2263,6 +2263,21 @@ declare module _ {
 		object: any,
 		whereValue: Dictionary<any>): string;
 
+	/**
+	* Iterates over own and inherited enumerable properties of an object, executing the callback for 
+	* each property. The callback is bound to thisArg and invoked with three arguments; (value, key, 
+	* object). Callbacks may exit iteration early by explicitly returning false.
+	* @param object The object to iterate over.
+	* @param callback The function called per iteration.
+	* @param thisArg The this binding of callback.
+	* @return object
+	**/
+	export function forIn<T extends {}>(
+		object: Dictionary<T>,
+		callback?: ObjectIterator<T, void>,
+		thisArg?: any): Dictionary<T>;
+
+
 	/**
 	* Recursively merges own enumerable properties of the source object(s), that don't resolve 
 	* to undefined into the destination object. Subsequent sources will overwrite property