docs: remove bad documentation

fixes #27

README.md

@@ -69,10 +69,6 @@ The options can also contain any of the follow (for the full list, see [cookies
   - `signed`: a boolean indicating whether the cookie is to be signed (`false` by default). If this is true, another cookie of the same name with the `.sig` suffix appended will also be sent, with a 27-byte url-safe base64 SHA1 value representing the hash of _cookie-name_=_cookie-value_ against the first [Keygrip](https://github.com/expressjs/keygrip) key. This signature key is used to detect tampering the next time a cookie is received.
   - `overwrite`: a boolean indicating whether to overwrite previously set cookies of the same name (`false` by default). If this is true, all cookies set during the same request with the same name (regardless of path or domain) are filtered out of the Set-Cookie header when setting this cookie.
 
-### Session.isNew
-
-  Is `true` if the session is new.
-
 ### Destroying a session
 
   To destroy a session simply set it to `null`: