Implement logout.
export const ADD_NOTE = 'ADD_NOTE';
export const ADD_NOTE_ASYNC = 'ADD_NOTE_ASYNC';
export const LOAD_NOTES_BY_SESSION = 'LOAD_NOTES_BY_SESSION';
export const LOAD_NOTES_BY_SESSION_ASYNC = 'LOAD_NOTES_BY_SESSION_ASYNC';
export const CREATE_SESSION = 'CREATE_SESSION';
export const CREATE_SESSION_ASYNC = 'CREATE_SESSION_ASYNC';
export const UPDATE_SESSION = 'UPDATE_SESSION';
export const UPDATE_SESSION_ASYNC = 'UPDATE_SESSION_ASYNC';
export const LOAD_SESSIONS = 'LOAD_SESSIONS';
export const LOAD_SESSIONS_ASYNC = 'LOAD_SESSIONS_ASYNC';
export const AUTH_LOGIN_SUBMIT = 'AUTH_LOGIN_SUBMIT';
export const AUTH_LOGIN_REQUEST = 'AUTH_LOGIN_REQUEST';
export const AUTH_LOGIN_SUCCESS = 'AUTH_LOGIN_SUCCESS';
export const AUTH_LOGIN_ERROR = 'AUTH_LOGIN_ERROR';
export const AUTH_STORE_TOKEN_ASYNC = 'AUTH_STORE_TOKEN_ASYNC';
export const AUTH_STORE_TOKEN = 'AUTH_STORE_TOKEN';
export const AUTH_LOGOUT = 'AUTH_LOGOUT';