Update README

README.rst

@@ -41,6 +41,10 @@ called twice with the same set of arguments, the result from the first call
 will be reused for the second, unless the file pointed to by ``path`` changes,
 in which case the function will be run again.
 
+``memoize_path()`` optionally takes an ``exclude_kwargs`` argument, which must
+be a sequence of names of arguments of the decorated function that will be
+ignored for caching purposes.
+
 Caches are stored on-disk and thus persist between Python runs.  To clear a
 given ``PersistentCache`` and erase its data store, call the ``clear()``
 method.