Add blank line before class's docstring.

Closes #358
diff --git a/README.rst b/README.rst
index 6cbd0ce..6abb80d 100644
--- a/README.rst
+++ b/README.rst
@@ -301,6 +301,9 @@
             def method():
                 pass
 
+``BLANK_LINE_BEFORE_CLASS_DOCSTRING``
+    Insert a blank line before a class-level docstring.
+
 ``COALESCE_BRACKETS``
     Do not split consecutive brackets. Only relevant when
     ``DEDENT_CLOSING_BRACKETS`` is set. For example: