Overflow correctly for addresses
Overflow correctly for addresses

I wouldn't say this is correct per se - I would much rather throw an
error than ignore the first hex digit, but apparently the simulator does
this.

Closes #24

lorderikir/MARIE.js,MARIE-js/MARIE.js,MARIE-js/MARIE.js,lorderikir/MARIE.js,MARIE-js/MARIE.js,lorderikir/MARIE.js