Dragging on Retina MacOSX

[Xrave]

I'm running into an issue where dragging tabs causes a chunk of other tabs (above it or under, depending on direction of drag) to slide to the left or the right. I'll debug it more when I have time, but just filing a issue report right now.

There are also very heavy conflict issues when there are two firefox windows. Themes and "Display Tabs on right" doesn't always work and does not usually apply to both windows.

System: Macbook Pro Retina

All behaviors restored after a restart. You should probably ask users to restart their browsers after installing 👍

Loving this fork so far. Thank you so much for this!

Xiaonan