Update cachematrix.R

1. The submitted URL points to a GitHub repository
2. The R file contains code implementing the complete assignment
3. Both functions have corresponding explanatory comments in the R file
4. The 'makeCacheMatrix' function appears to be correct and is written in a well-formatted and easily readable style
5. The 'cacheSolve' function appears to be correct and is written in a well-formatted and easily readable style