Saddle-points: Add test for multiple saddle-points in a row

[DocFogel]

There is a test for multiple saddle points in a column, but there is no test for multiple points in a row.

These changes rename the existing test to indicate it tests for saddle points in a column and adds a test for multiple points in a row.

[cmccandless]

Exercise description

[rpottsoh]

Thanks for making the change.

What caused you to consider adding the new test case? There was no initial comment to your PR to give some background about what brought about the proposed change.

[DocFogel]

I was mentoring a student and the initial solution missed this case. I realized it from reading the code, so I deviced the test and verified that the code failed.
The student added yet another test where the whole matrix was actually full of saddle-points, but I think this test and the existing one, checking for multiples in a column, covers that scenario too.

[rpottsoh]

@DocFogel thanks for the background information. Nice find! I have gone ahead and borrowed your initial comment from your exercism/python#1427 comment so others that may come across this PR in the future will have a better idea behind the PR's purpose.

[rpottsoh]

I think this is ready for merging, but I will hold off at least another day, to allow anyone else a chance to provide any input they might like to give. If someone else wants to merge sooner that is OK too.