Implemented "==" operator in compiler and fixed comparisons instruction in VM.

Signed-off-by: Christian Gunderman <christian@sonofboss.cwru.edu>
Implemented "<" operator and switched OP_LT operand order in VM.

Signed-off-by: Christian Gunderman <christian@sonofboss.cwru.edu>
Implemented ">=", "<=" operators.

Signed-off-by: Christian Gunderman <christian@sonofboss.cwru.edu>