old version of pandas requirement

[Daniel-Foyt-UCSF-Berkeley]

There is a requirement for an old version of the Pandas module in requirements.txt. Might be easier to use if you use minimum versions instead i.e pandas >= 0.25.3 unless the new version is not compatible. They only updated it a couple months ago.

[davidbrown2324]

I agree. I won't change this yet because I want to finish the test suite before I make any changes. For users installing now, I would recommend using a virtual environment, so it shouldn't matter. But I agree these should be converted to a minimum once the tests can confirm it works with the latest versions (which I am sure they will).

@Huanglab-ucsf if anyone wants to submit the change as a pull request that would be totally welcome.