Evaluate with resultant output
Evaluate with resultant output

This includes 'evaluate' function to parse the abstract syntax
tree along with 'evaluate_o' function which performs the
respective operator's function. After all this, the output is
printed. Printing of abstract syntax tree is not removed to aid
development while this is in pre-alpha stage.

Mr-Kumar-Abhishek/zuzeelik,shadow-stranger/zuzeelik