Change to include gaussj

To include gauss jordan elimination
the file was modified accordingly.
Testing Gauss Jordan elimination

main was modified to test GaussJordan()
function.
Gauss Jordan Elimination

Gauss Jordan elmination for solving linear
equations has been added. The function takes
two input matrices A and b where A is a
n-by-n matrix and b is n-by-m matrix. It
destroys the input matrix and subsequently
stores the inverse of A in A and the solution
in b.