Add Corrfunc/tests.py to CI testing

[lgarrison]

From #258, we're calling the linear binning tests from Corrfunc/test.py, but it isn't CI'd. This PR starts CI-ing it.

An alternative would be to move the linear binning tests to [theory|mocks]/python_bindings/call_correlation_functions.py or a new file in the same directory. But following the "principle of least surprise", I think it makes sense to just CI Corrfunc/test.py, as most users/devs will expect it to be tested.

This is a blocking issue for #258, as we aren't actually testing anything yet!

[manodeep]

Hmm - does the CI only on master run rather than that on the branch? In which case, perhaps I will just have to merge this directly without the GH CI running

[lgarrison]

The CI did run on the first commit in this PR, and then the second was just a changelog update so I did [ci skip] out of habit 😬. But it passed all the checks in the first commit, so as long as my changelog update wasn't too reckless, it should be safe to merge!

[manodeep]

Ahh yes - I now see that the CI ran under the Actions tab (rather than the checks tab associated with the PR). Looks good to me :)