Add branchOn
Merge branch 'master' of github.com:ksundberg/CS6300 into class2
Fix register allocation

The used statement needs to come after the slt for register allocation
to work properly. We were setting this in the used set initially for a
block when it was necessary to add it at the 'end' of a block only.
Add stop statement at end of program
Merge pull request #22 from ostlerc/class2

Fix register allocation