Merge pull request #12 from agiliq/Chapter7module5edit

misprint of a word

docs/uneditable_existing.rst

@@ -1,7 +1,7 @@
 How to make a field editable while creating, but read only in existing objects?
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
-YOu need to make the :code:`name` and :code:`category` read only once a :code:`Hero` is created. However duing the first write the fields needs to be editable.
+You need to make the :code:`name` and :code:`category` read only once a :code:`Hero` is created. However duing the first write the fields needs to be editable.
 
 You can do this by overriding :code:`get_readonly_fields` method, like this::