Jslint+cookiefix+html5slider

Used jslint on the code and removed a lot of linting-errors.

The `lastframe`-cookie overwrote the `?frame=`-Get-Parameter. Fixed that too.

I also included the html5slider and fixed it for firefox. (Couldn't find any flaws now)

Wanted to split this over some pull requests, but at some point i had to fix an error, i already fixed in another branch, so you get one big pull request.

I used a code-snippet from [1] to normalize the scroll-event. This also handles horizontal scrolls, so it might fix https://github.com/deplicator/xkcdTime_atyourownpace/issues/12, but i can not test, because i do not own a Mac.

[1] https://developer.mozilla.org/en-US/docs/DOM/Mozilla_event_reference/wheel?redirectlocale=en-US&redirectslug=Mozilla_event_reference%2Fwheel