Fix the != comparison for SectionPage

Fixes #10

Because MkDocs' base classes define this operation, the implicit definition does not kick in, and the result is always wrong.

Either this or mkdocs/mkdocs#2735 would fix it.

Author: oprypin

mkdocs_section_index/__init__.py

@@ -20,5 +20,8 @@ def __repr__(self):
     def __eq__(self, other):
         return object.__eq__(self, other)
 
+    def __ne__(self, other):
+        return not (self == other)
+
     def __hash__(self):
         return object.__hash__(self)