[firebase] logout user

[Costas]

				//logout
				$("#logout").on('click', function(e) {
					var firebaseRef = new Firebase("https://" + baseURL);

					var auth = new FirebaseSimpleLogin(firebaseRef, function(error, user) {
						if (error | user === null)
							window.location = "index.html";
						else
							auth.logout();
					});
				});