Mishmash of fixes, enhancements, and cleanups

Includes various bug fixes, enhancements, and cleanups, including:

- [x] moves `ktkGetNextDate` out of the global namespace
- [x] removes stray alert + accidental click handler corruption
- [x] fixes `dateDeserialize` to allow dates before 1970
- [x] fixes & robustifies cross-browser mouse wheel detection
- [x] adds check for `$.cookie` if `useCookie` option set to `true`
- [x] optimizes PNGs (via smush.it)
- [x] updates jshint options
- [x] points out some unused variables (for future cleanup efforts)

(Goes without saying, please test this before accepting. ;)