Rename order_by.

Author: WaVEV

django_mongodb/query.py

@@ -169,7 +169,7 @@ def join(self, compiler, connection):
     return lookup_pipeline
 
 
-def orderby(self, compiler, connection):
+def order_by(self, compiler, connection):
     return self.expression.as_mql(compiler, connection)
 
 
@@ -238,5 +238,5 @@ def where_node(self, compiler, connection):
 def register_nodes():
     Join.as_mql = join
     NothingNode.as_mql = NothingNode.as_sql
-    OrderBy.as_mql = orderby
+    OrderBy.as_mql = order_by
     WhereNode.as_mql = where_node