Slower scrolling, prevent navjump, prevent scrolljump, fonts for Polish

Bug 822344 - slow down scrolling when covering longer distances
Bug 831332 - switch to Georgia for Polish (Vollkorn lacks characters)
Bug 822341 - pad body to minimize visible jump when modal overlay disables scrollbars
Optimized promo video thumbnail
Added classes for Czech and Russian font switch
Using Math.abs for scrollTime

Also added an else to set scrollTime back to 1000 for short scrolls. Probably a cleaner way.
Added body class for Slovenian
Add links to creative brief

Also added play button to video thumbnails
Bug 831323 - expanded font stack for zh-TW and zh-CN
Merge pull request #127 from craigcook/add-creative-brief

Add links to creative brief, play buttons, fonts for zh-TW and zh-CN