DOCS-469: adding version change information to elemMatch projection operator

Author: Sam Kleinman

source/reference/projection/elemMatch.txt

@@ -8,16 +8,18 @@ $elemMatch (projection)
 
 .. projection:: $elemMatch
 
+   .. versionadded:: 2.2
+
    Use the :projection:`$elemMatch` projection operator to limit the
    response of a query to a single matching element of an
    array. Consider the following:
 
-   .. example:: 
+   .. example::
+
+      Given the following document fragment:
 
-      Given the following document fragment: 
-      
       .. code-block:: javascript
-      
+
          {
           _id: ObjectId(),
           zipcode: 63109
@@ -27,24 +29,24 @@ $elemMatch (projection)
                        { name: "jeff", school: 108, age: 15 }
                       ]
          }
-     
-      Consider the following :method:`find() <db.collection.find()>` 
+
+      Consider the following :method:`find() <db.collection.find()>`
       operation:
 
       .. code-block:: javascript
-   
-         db.students.find( { zipcode: 63109 }, 
-                           { _id: 0, 
+
+         db.students.find( { zipcode: 63109 },
+                           { _id: 0,
                              dependents: { $elemMatch: { school: 102 } } } )
 
       The query would return all documents where the value of the
       ``zipcode`` field is ``63109``, while the projection excludes
       the ``_id`` field and only includes those elements of the
       ``dependents`` array where the ``school`` element has a valueof
       ``102``. The documents would take the following form:
-   
+
       .. code-block:: javascript
-       
+
          {
           dependents: [
                        { name: "john", school: 102, age: 10 },