Added session expiration tests and more
Renamed 'tokenTtlCheckFreqencyMs' to 'tokenTtlCheckIntervalMs' in readme, index, and tests
Added 'sessionTimeoutCheckIntervalMs'
Added unauthenticate() call on 'expire' event
Renamed 'fakeSecretToken' to 'fakeToken' in testTtl.js
Added 'fakeTokenData' in testTtl.js