This homework requires implementation of class Vector.
The declaration of the Vector class can be found in vector.h.
Methods are already listed, but do not yet work.
The second class matrix (in matrix.h) is fully implemented and
can be used as a source of ideas.
Main program program matrix.cc is tests Matrix-Vector operations,
Matrix-Matrix operations and Speed of the computer.
If your computer is slow when testing speed, reduce Nmax by changing
1e8 to something smaller.
You can also reduce maximum matrix size (if matrix does not fit to
the RAM) by decreasin maxiumu matrix size which is now set to 2000.