Create 3o2.1.antisymmetric_square.py

# By Dimitris_GR from forums
# Modify Problem Set 31's (Optional) Symmetric Square to return True 
# if the given square is antisymmetric and False otherwise. 
# An nxn square is called antisymmetric if A[i][j]=-A[j][i] 
# for each i=0,1,...,n-1 and for each j=0,1,...,n-1.