Fixed <<remember>>

* Fixed the code so that it works - and, more specifically, can remember
multiple variables given in a single compound statement to one macro.
* Added <<forget>>, as seen in T.M.Edwards's SugarCube.
* Removed the cookie fallback. No browser that Twine 1 currently
supports (IE 8 upward) lacks localStorage.
* Also fixed a few minor bugs with other macros.