Added LoopingCall construct
Ported functionality for tracking term state and enabling SIGTSTP...

from pyamp.
Updated zebra example to show Dad more stuff
Added unbuffered input handling ported from pyamp
Added Keyboard helper class to terminal.py...

preparing to handle input (all this stuff is ported from Pyamp)
Made Terminal class automatically handle SIGTSTP...

overrideable, natch
Fixed SIGTSTP behaviour