Flowplayer styles improved to work better with aspect ratios different from the default.

Based on: http://alistapart.com/article/creating-intrinsic-ratios-for-video
```sass
$video-aspect-ratio-wide: 9 / 16 !default
$video-aspect-ratio-four-three: 3 / 4 !default

// default
padding-bottom: $video-aspect-ratio-wide * 100%
&.four-three
    padding-bottom: $video-aspect-ratio-four-three * 100%
```