Document new exception.

Lukasa · Lukasa · commit 8554a84b6899 · 2016-08-03T14:31:04.000+01:00
diff --git a/docs/source/api.rst b/docs/source/api.rst
@@ -17,3 +17,5 @@ Exceptions
 .. autoclass:: priority.DuplicateStreamError
 
 .. autoclass:: priority.MissingStreamError
+
+.. autoclass:: priority.TooManyStreamsError
