Ensure callback shorthands work with _.uniq. [\ht @jden, @motowilliams]

Former-commit-id: d9a0e688414edc4167b5f8e9ca123bab587f8264

test/test.js

@@ -2610,6 +2610,18 @@
 
       deepEqual(actual, expected);
     });
+
+    _.each({
+      'an object': ['a'],
+      'a number': 0,
+      'a string': '0'
+    },
+    function(callback, key) {
+      test('should work with ' + key + ' for `callback`', function() {
+        var actual = _.uniq([['a'], ['b'], ['a']], callback);
+        deepEqual(actual, [['a'], ['b']]);
+      });
+    });
   }());
 
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