Switch rate metric display to ms/frame, which is more useful
Switch from tremor back to libvorbis for performance

It turns out that tremor is actually significantly slower in the
JS virtual machine on slower devices like an iPod Touch 5th-generation.
A *lot* of time gets spent in the integer multiplication functions.

Going back to vorbis shaved a ~60ms per-frame decode time down to ~40ms
or less on the iPod on the 160p/15fps videos.
Optimize YUV output for 4:2:0 slightly more

We were only doing one line at a time, but we can save a little
math by doing two lines at a time.

Shaves per-frame drawing time at 160p on iPod Touch from about
10ms down to about 8ms.
yuv 4:2:0 - save some more common factors

shaves another ms/frame off of drawing on iPod Touch
Shave another teeny tiny bit off the 4:2:0 yuv conversion

don't really need to keep track of xdec, just incrememnt them pointers
Optimize 4:2:0 yuv loop slightly more!

Shaves another 0.8ish ms from iPod Touch 160p playback
Get Math.floor() out of resampling hot path

|0 does the same thing but doesn't add up on the profiler in IE
show a rolling average frame time instead of lifetime average
Fix benchmark scale to 2x target frame rate, remove 30fps line
show correct message on error
simple pause/resume
update playback time at buffer head even when starved
use right sample rate for calcs
Merge branch 'master' into decoder-worker