Remove token and user id keys from session and local storage on logout

Remove 'accessTokenId' and 'currentUserId' keys from session and local storage on logout.
Fixes #61 
I've kept those lines and, in fact, introduced a completely different ```it(...)``` clause in tests without affecting any of the previous tests.

I'm sorry, I'm not sure what you mean by *... If you keep an empty value, the test will fail if it checks wrong item names.* Please elaborate.