added initial calculator files and makefile
Shortened executible name to 'calc' for faster typing
Recursive calculator is fully functional now with arithmetic between integers of mixed signs
Changed makefile so it deletes the executable 'calc' since the name change
Fixed issue with cin storing info in more than one variable. Also fixed infinite loop on incorrect input. Mathematical operations still function as expected. Annotations in both calculator.cpp and main.cpp were added for better explanation of logic