Update cachematrix.R

First version of EF. Checked in R Studio, as you can see here:

> myMat$set(matrix(c(1,24,13,41,53,62,71,88,93),nrow=3,ncol=3))
> cacheSolve(myMat)
            [,1]        [,2]        [,3]
[1,] -0.04545455  0.05080214 -0.01336898
[2,] -0.09384164 -0.07158875  0.13938244
[3,]  0.06891496  0.04062446 -0.08030016
> cacheSolve(myMat)
getting cached data
            [,1]        [,2]        [,3]
[1,] -0.04545455  0.05080214 -0.01336898
[2,] -0.09384164 -0.07158875  0.13938244
[3,]  0.06891496  0.04062446 -0.08030016