Implementation of prime function

Complier went wrong. Couldn't test it.
#include <iostream> and implement defix function

Couldn't run the file, so I have no idea whether my implementation is
right or not.
Answer the five questions
Successfully tested prime function
Successfully tested defix function
Successfully tested sumSlice function
Successfully tested listPrime function
Starting working on square function

Since I don't know how to use 2 dimensional array, I would focus on
printing out what I want.
Starting with special case

printing out what I want when side length is equal to 1 or 2
Starting on working on general cases

Fixed the little layout problem in the two special cases.
Successfully implemented square function

Haven't tested it with too much data, but I'll definitely get the
testing done before the deadline.
Made all possible kinds of testing on Square

They turn out good!
Updated the status of my functions

Also, I revised my answers to some questions. Hopefully they look good.
Merge pull request #24 from YangLi1/master

Success!