Update page.py (#57)

Noticed a typo in "Expected" on line 73

flask_flatpages/page.py

@@ -70,6 +70,6 @@ def meta(self):
         if not meta:
             return {}
         if not isinstance(meta, dict):
-            raise ValueError("Excpected a dict in metadata for '{0}', got {1}".
+            raise ValueError("Expected a dict in metadata for '{0}', got {1}".
                              format(self.path, type(meta).__name__))
         return meta