Add DEN view tests

[KyleVaughn]

Description:

Add a test to check the view method/function is implemented correctly

Tasks:

• [ ] Coordinate with the person implementing dense view method to know the interface
• [ ] Ensure that view method is defined (void DEN_view(double **A, const size_t nrows, const size_t ncols))
• [ ] Understand the i/o of view method
• [ ] Initialize a small dense matrix as a view test and pass it to DEN_view method
• [ ] Compare the output "DEN_matrix.out" with desired output (including spaces and brackets)
• [ ] Check the values in output is same as expected up to desired accuracy (assign an error threshold--L1 or L2 norm)
• [ ] Print the output message of success or failure based on the error tolerance

Definition of done:

View test is implemented when it works successfully and prints correct output message.

[KyleVaughn]

Review by @webberqu417

[webberqu417]

The tasks are well planned out for this issue. I would consider being a little more specific on the small dense matrix for testing. Where will this come from? Are you going to generate one yourself or read from example files that we have been provided?