Fix a regression from 3cd0487 (close #2777)

Author: jgonggrijp

modules/index.js

@@ -805,6 +805,7 @@ export var bindAll = restArguments(function(obj, _keys) {
     var key = _keys[index];
     obj[key] = bind(obj[key], obj);
   }
+  return obj;
 });
 
 // Memoize an expensive function by storing its results.

test/functions.js

@@ -99,7 +99,8 @@
       sayHi: function() { return 'hi: ' + this.name; }
     };
     curly.getName = moe.getName;
-    _.bindAll(moe, 'getName', 'sayHi');
+    var bound = _.bindAll(moe, 'getName', 'sayHi');
+    assert.strictEqual(bound, moe, 'returns the bound object');
     curly.sayHi = moe.sayHi;
     assert.strictEqual(curly.getName(), 'name: curly', 'unbound function is bound to current object');
     assert.strictEqual(curly.sayHi(), 'hi: moe', 'bound function is still bound to original object');