Correctly move cursor by count if provided.
Update pry, remove pry-nav.
Add cursor setting on per interface basis.
Reincarnate Buffer ready for interface copying work.
Add tests.
Add #update method;

On each event loop, we will call the update method of each interface so that it can flush output to the screen if it has changed. I’m not sure exactly how this mechanism will work yet, but I envisage a poor man’s double buffer.