just need to practice a little

Added a short description and code to save the working directory then
set it to the location of the R stub code provided for the assignment.
The final line of the code will reset the working directory to original.

Using the stub code and example provided, the code was modified to
create and then solve for the inverse of a square (invertible) matrix,
store the inverse and then check for solution in subsequent calls for
the inverse instead of re-solving the inverse.

Modified the stub and code and example to create a square (invertible)
matrix, from a function, check to see if the inverse was calculated and
either return the previously save inverse, or calculating and saving the
inverse.

Refined stub and example code to execute as desired, out putting inverse
of a matrix after first determining if a it was previously calculated
and then either
print out the saved inverse or calculates it and prints it out. Also
added a detailed explanation of the functions.