Update cachematrix.R

Tested on my comp and it works:
> g<-makeCacheMatrix(matrix(c(1,6,11,21),2,2))
>cacheSolve(g)
           [,1]        [,2]
[1,] -0.4666667  0.24444444
[2,]  0.1333333 -0.02222222
>> cacheSolve(g)
getting cached data
           [,1]        [,2]
[1,] -0.4666667  0.24444444
[2,]  0.1333333 -0.02222222