Fix heading hierarchy in debugging guide
@@ -31,7 +31,7 @@ which matchers didn't match. This can help you with debugging custom
matchers.
CannotOverwriteExistingCassetteException
-========================================
+----------------------------------------
When a request failed to be found in an existing cassette,
VCR.py tries to get the request(s) that may be similar to the one being searched.
