Update README.md to clarify that depth-first traversal should be done in-order

Author: seanchen1991

README.md

@@ -28,13 +28,17 @@ It is recommended that you allot about 1 and a half hours for this portion of th
 
 Navigate into the `ex1` directory in the `data_structures` directory. Inside, you'll see the `binary-search-tree.py` file with a complete implementation of the binary search tree class. Your first task is to implement either `depth_first_for_each` or `breadth_first_for_each` on the `BinarySearchTree` class:
 
-   * `depth_first_for_each(cb)` receives an anonymous function as a parameter. It should then execute the anonymous function on each node in the tree in [depth-first](https://en.wikipedia.org/wiki/Depth-first_search) order. Your task is to implement the logic to traverse the tree in the desired order. Remember that the anonymous function is supplied by the caller of the method. All you have to do is ensure that the anonymous function is being called on each tree node in the desired order.
+   * `depth_first_for_each(cb)` receives an anonymous function as a parameter. It should then execute the anonymous function on each node in the tree in [depth-first](https://en.wikipedia.org/wiki/Depth-first_search) order. Your task is to implement the logic to traverse the tree in depth-first in-order fashion (as opposed to pre-order or post-order). Note that the pseudocode showcased on the Wikipedia article traverses the tree in-order. 
+
+   * Remember that the anonymous function is supplied by the caller of the method. All you have to do is ensure that the anonymous function is being called on each tree node in the desired order.
 
      _HINT_: In order to achieve depth-first order, you'll probably want to utilize a Stack data structure. 
 
      * Run `python test_depth_first_search.py` to test your depth-first search implementation.
 
-   * `breadth_first_for_each(cb)` receives a callback function as a parameter. It should then execute the anonymous function on each node in the tree in [breadth-first](https://en.wikipedia.org/wiki/Breadth-first_search) order. Your task is to implement the logic to traverse the tree in the desired order. Remember that the anonymous function is supplied by the caller of the method. All you have to do is ensure that the anonymous function is being called on each tree node in the desired order.
+   * `breadth_first_for_each(cb)` receives a callback function as a parameter. It should then execute the anonymous function on each node in the tree in [breadth-first](https://en.wikipedia.org/wiki/Breadth-first_search) order. Your task is to implement the logic to traverse the tree in left-to-right breadth-first fashion.
+   
+   * Remember that the anonymous function is supplied by the caller of the method. All you have to do is ensure that the anonymous function is being called on each tree node in the desired order.
 
      _HINT_: In order to achieve breadth-first order, you'll probably want to utilize a Queue data structure.