Remove all mention of order-by-expression from docs (for now)

Author: Stuart McGrigor

README.md

@@ -135,7 +135,6 @@ Attributes of angular treecontrol
     - `label` : inhject classes into the div element around the label
     - `labelSelected` : inject classes into the div element around the label only when the node is selected
 - `order-by` : value for ng-repeat to use for ordering sibling nodes
-- `order-by-expression` : expression for ng-repeat to use for ordering sibling nodes
 - `reverse-order` : whether or not to reverse the ordering of sibling nodes based on the value of `order-by`
 - `filter-expression` : value for ng-repeat to use for filtering the sibling nodes
 - `filter-comparator` : value for ng-repeat to use for comparing nodes with the filter expression

index.html

@@ -943,7 +943,7 @@ <h1>Sorting tree nodes <small>(order-by, reverse-order)</small></h1>
             </div>
         </div>
         <div class="col-md-6">
-            <p>The <code>order-by</code>, <code>order-by-expression</code> and <code>reverse-order</code> properties allows
+            <p>The <code>order-by</code> and <code>reverse-order</code> properties allows
 	      controlling the sorting of the tree nodes.
                 The value of those attributes is used with the <code>ng-repeat</code> orderBy filter -
                 see more details at the <a href="https://code.angularjs.org/1.2.0-rc.3/docs/api/ng.filter:orderBy">Angular JS orderBy</a> docs.</p>