Remove `future` dependency to address CVE-2022-40899

[regolith]

Seeing a new CVE on the scanners: CVE-2022-40899

The future library is only used here in one place, and there is already a PR #23 to remove it. This is my only third party dependency on future, so it would be very helpful if you could cut a new release without it. Thanks!

[robert-mings]

Hey @regolith, we recently removed the future dependency in #45. Please update to v1.2.5 to capture these changes. Closing now.