Add command-line arguments.
Implement JP + V0 and RND
Implement SNE (register arguments) and LD for the I register
Implement register arithmetic instructions.
Implement SE (register arguments) and LD
Implement CLS, RET, SYS, JP, and CALL
Implement program loading.
Calculate label positions relative to load address
Add initial SDL bindings.
Improve error messages for invalid arguments.
Remove support for labels where not necessary.
Implement remaining instructions.
Implement SUBN instruction.
Implement SUB instruction.