Added get_rows and get_cols method
Added basic mathematical operations

Basic mathematical operations like addition and subtraction
were added for the matrix.
Implemented basic operations.

Implemented the basic operations addition and subtraction.
Added methods for display and scalar multipy

Method to multiply a matrix with a scalar has been added alond with a
function to display a matrix. The display function is useful for testing
and debug purposes. A few minor corrections were made to the existing
methods for basic arithmetic. All the code related to testing resides in
main.cpp.