Document some register attributes (#417)

* Document some register attributes

* HistoricalRecords isn't a model

* Remove empty last line

Author: dgilge

docs/advanced.rst

@@ -64,6 +64,23 @@ third-party apps you don't have control over.  Here's an example of using
 
     register(User)
 
+If you want to separate the migrations of the historical model from those of
+the third-party model itself you can pass a module as ``app`` attribute to
+``register``. For instance, if the migrations shall live in the migrations
+folder of the package you register the model in, you could do:
+
+.. code-block:: python
+
+    register(User, app=__package__)
+
+You can pass attributes of ``HistoricalRecords`` directly to ``register``:
+
+.. code-block:: python
+    
+    register(User, excluded_fields=['last_login']))
+
+For a complete list of the attributes you can pass to ``register`` we refer
+to the source code.
 
 Allow tracking to be inherited
 ---------------------------------
@@ -428,4 +445,4 @@ This may be useful when you want to construct timelines and need to get only the
     new_record, old_record = p.history.all()
     delta = new_record.diff_against(old_record)
     for change in delta.changes:
-        print("{} changed from {} to {}".format(change.field, change.old, change.new))
+        print("{} changed from {} to {}".format(change.field, change.old, change.new))