Incomparability issue with numpy 1.20.0

[weixuanfu]

After comparing the CI builds passed last week with ones failed this week, I found that numpy was updated from 1.19 to 1.20 on Jan 30, 2021. I think it is the reason of failed CI builds. I pushed this commit 945fe3c459b578e9c9540209f088e846171c52c6 to coveralls branch to check if this can fix CI build.

[weixuanfu]

GitHub Action build passed after adding this commit.

[jay-m-dev]

I have confirmed that upgrading to numpy 1.20 causes errors. Version 1.19.5 is the latest version the currently works. See related (issue #481)[https://github.com/EpistasisLab/Aliro/issues/481]. Numpy will be updated further than 1.19.5 only when absolutely necessary to upgrade.