Break TWI_vect out into its own file so I can hand-optimize the assembly
gcc doesn't do a very good job of this, it pushes registers unnecessarily.
Fool only the parts we REALLY care about...
For some reason passing TW_STATUS to another function doesn't work. Grumble.
I can't tell if this works or not :(
Staggered brightness levels. Yay!
Maybe this is faster.