Clarifications for binary-search-tree exercise (#342)

exercises/practice/binary-search-tree/.docs/instructions.append.md

@@ -0,0 +1,12 @@
+# ignore
+
+## CoffeeScript specific instructions
+
+A BinarySearchTree instance must have 3 properties: `data`, `left` and `right`.
+
+An instance must have these methods:
+
+* `insert` which adds a new piece of data to the tree. This will add a new "leaf" node somewhere in the tree.
+* `each` that takes a "callback" argument. That is a function that will be called on _each piece of data_ in the tree **in order**.
+
+This exercise is a great place to practice **recursion**.

exercises/practice/binary-search-tree/binary-search-tree.coffee

@@ -4,6 +4,6 @@ class BinarySearchTree
 
   insert: (args) ->
 
-  data: ->
+  each: (callback) ->
 
 module.exports = BinarySearchTree