Remove stale sessions when updated

Remove stale sessions when posting a new session.
Set the cookie to an empty string with a past date when deleting a session.
adding moment as dependency
extending cookie expiry to 2 weeks, tests for expiry day
extending cookie expiry to 2 weeks, tests for expiry day
Merge branch 'patch-1' of git://github.com/tracker1/headrest into tracker1-patch-1
tests for cookie expiry patch
removing portion of patch that does session removal on post if session exists
Merge branch 'tracker1-patch-1' into cookies
changelog and version bump
Merge branch 'cookies'